Insight into Romanian Wild-Grown Heracleum sphondylium: Development of a New Phytocarrier Based on Silver Nanoparticles with Antioxidant, Antimicrobial and Cytotoxicity Potential

Abstract

Background: Heracleum sphondylium, a medicinal plant used in Romanian ethnopharmacology, has been proven to have remarkable biological activity. The escalating concerns surrounding antimicrobial resistance led to a special attention being paid to new efficient antimicrobial agents based on medicinal plants and nanotechnology. We report the preparation of a novel, simple phytocarrier that harnesses the bioactive properties of H. sphondylium and silver nanoparticles (HS-Ag system). Methods: H. sphondylium’s low metabolic profile was determined through gas chromatography–mass spectrometry and electrospray ionization–quadrupole time-of-flight–mass spectrometry. The morphostructural properties of the innovative phytocarrier were analyzed by X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, dynamic light scattering, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The antioxidant activity was evaluated using total phenolic content, ferric reducing antioxidant power, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) in vitro assays. The antimicrobial activity screening against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli was conducted using the agar well diffusion method. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay estimated the in vitro potential cytotoxicity on normal human dermal fibroblasts (NHDF) and cervical cancer (HeLa) cells. Results: A total of 88 biomolecules were detected, such as terpenoids, flavonoids, phenolic acids, coumarins, phenylpropanoids, iridoids, amino acids, phytosterols, fatty acids. The HS-Ag phytocarrier heightened efficacy in suppressing the growth of all tested bacterial strains compared to H. sphondylium and exhibited a significant inhibition of HeLa cell viability. Conclusions: The new HS-Ag phytocarrier system holds promise for a wide range of medical applications. The data confirm the capacity to augment the pertinent theoretical understanding in the innovative field of antimicrobial agents.

1. Introduction

Heracleum sphondylium (Apiaceae family), commonly known as hogweed or cow parsnip, is widespread in Europe, parts of Asia, and northern Africa, and is present throughout Europe except for in the extreme north and some Mediterranean regions [1,2,3,4,5]. In Romania, H. sphondylium, known locally as Brânca ursului, is common nationwide in various forms, frequent from lowlands to mountainous regions, in thickets, hayfields, meadows, riparian zones, sparse forests, and rocky grasslands [4,6,7]. The species exhibits high variability, leading to many mentioned subspecies (nine in European flora, three in Romanian flora) [4,5,6,7].

H. sphondylium is a biennial or perennial species with a thick, branched rhizome. The aerial stem is well developed, reaching heights of up to (150–) 200 (–350) cm and a 4–20 mm diameter. The leaves are highly variable, ranging from simple, undivided, or merely lobed to pinnatisect leaves with 3–5(7) asymmetrical, diversely lobed segments; the axil of the stem leaves is slightly swollen, rough-pubescent, or glabrous. The inflorescences are large, with umbels up to 25 cm in diameter, with up to 40 unequal rays, and with few or without bracts. The flowers have variously colored petals (white, yellow, pink, purple, greenish, or blue) and are often slightly pubescent externally. The ovary is glabrous, pubescent, or hispid. The fruits are strongly flattened, ellipsoidal, obovate, or nearly round, emarginate, with winged lateral ribs forming a delineated margin around them. The plants bloom from June to September [4,5,6,7].

H. sphondylium is used as a nutritional source in many regions globally; the stems, leaves, and inflorescences are utilized to obtain numerous preparations; e.g., in Eastern Europe and Northeastern Asia, various soups are made using this plant [1,2].

H. sphondylium roots, stems, leaves, and inflorescences are employed in traditional medicine in countries where it grows spontaneously to treat digestive disorders such as flatulence, dyspepsia, diarrhea, and dysentery, as well as hypertension, epilepsy, menstrual problems, and for wound healing, due to its analgesic, sedative, anti-infective, antioxidant, anticonvulsant, vasorelaxant, antihypertensive, carminative, tonic, and aphrodisiac properties [8,9,10,11,12,13,14].

Recent studies addressing the chemical composition of H. sphondylium have demonstrated the presence of a complex mixture of furocoumarins (bergapten, isopimpinellin, heraclenin), essential oil, polyphenolic compounds, phytosterols, pentacyclic triterpenes, and fatty acids [1,2,3,14,15,16,17]. Numerous studies reported multiple therapeutic properties, such as antioxidant, vasorelaxant, antimicrobial, antiviral, anti-inflammatory, antidiabetic, neuroprotective, and antitumor [1,12,13,14]. Despite its great pharmacological potential, most research focuses on several phytochemical categories extracted from different parts of this plant [1,12,13,14]. In addition, there is limited research on Romanian wild-grown H. sphondylium addressing only essential oil and phenolic compounds [8,16].

Furthermore, the variations in secondary metabolites amount to a function of various abiotic and biotic factors, growth stage, and extraction technique parameters (temperature, solvent polarity, duration, pH, etc.), which dictate the herb’s chemical profile and biological activity [18,19,20,21,22]. Conversely, recent research on natural compounds reported that several molecules exhibit low bioavailability due to reduced chemical stability and limited adsorption [23,24,25].

Antimicrobial resistance and tolerance emerge as paramount health concerns with severe repercussions on the therapeutic strategy of infectious diseases [24]. Antibiotic abuse or misuse for human health and the agri-food sector contributed significantly to rendering existing antimicrobials ineffective and exacerbating antimicrobial resistance. Without urgent measures, the depletion of antimicrobial alternatives will lead to a rise in infections related to antibiotic-resistant pathogens. It is urgent to identify new targeted antimicrobial agents against pathogenic microorganisms while mitigating the progression of antimicrobial resistance. Consequently, various strategies to overcome these challenges have been developed [25,26,27].

On the other hand, the implementation of nanotechnology in the biomedical field led to the development of advanced materials based on numerous phytoconstituents with high antimicrobial, antiviral, neuroprotective, and antitumor activity, which allowed researchers not only to overcome these constraints, but also to achieve a significant improvement in the pharmacological activity, controlled release, and specificity while minimizing toxicity [24,25,26,27,28].

To this end, various nanoparticles (NPs), such as platinum, silver, gold, iron oxide, titanium dioxide, zinc, silica, and copper, have been reviewed for biomedical applications [29]. Among these, the silver nanoparticles (AgNPs) stood out due to their broad applicative potential from bioengineering to diagnosis, detection, gene and drug delivery, vaccines, and antimicrobial agents to wound and bone treatment [29,30,31]. Their extensive growth development is due to their outstanding size-related physicochemical (size, shape, surface plasmon resonance, surface charge, high surface-to-volume ratio, chemical stability, low reactivity) and biological (antimicrobial) properties [30,31]. In addition, AgNPs display a uniquely tailored hydrophilic–hydrophobic balance through simple functionalization with various molecules, and the capability to cross the blood–brain barrier ensures the opening of new possibilities in the design of drug delivery systems and new performant antimicrobial agents [30,31,32]. In that sense, research on developing engineered herbal formulation assembles using NPs represents a significant advancement in enhancing the biological properties of phytoconstituents and enabling specific targeting and localization on surfaces [29].

This study investigates the preparation of a new phytocarrier through H. sphondylium loading with AgNPs (HS-Ag system) encompassing the physical and chemical characteristics and in vitro evaluation of its antioxidant, antimicrobial, and cytotoxicity potential. To the best of our knowledge, the low metabolic profile of H. sphondylium grown wild in Romania is reported for the first time in this study.

2. Results

2.1. GC–MS Analysis of H. sphondylium Sample

The compounds separated using gas chromatography–mass spectrometry (GC–MS) are depicted in Figure 1 and detailed in Table 1.

Figure 1.

Total ion chromatogram of H. sphondylium sample.

Table 1.

Main phytochemicals identified by GC–MS analysis of H. sphondylium sample.

No.	RT [min]	RI Determined	Area [%]	Compound Name	Ref.
1	3.13	821	1.18	2-hexenal	[33]
2	5.73	1021	0.86	p-cymene	[34]
3	6.39	938	1.52	α-pinene	[34]
4	9.65	1228	0.67	cuminaldehyde	[35]
5	7.87	1034	1.48	limonene	[34,36]
6	11.60	1488	4.43	β-ionone	[34,36]
7	12.46	988	3.36	myristicin	[37]
8	16.15	1090	0.61	linalool	[34,36]
9	17.14	1212	1.56	myrtenal	[38]
10	18.32	1843	4.51	anethole	[34]
11	19.42	1165	0.79	decanal	[39]
12	20. 09	1473	19.49	α-curcumene	[34]
13	21.43	1247	1.85	carvone	[34,36]
14	22.67	1663	3.42	apiole	[40]
15	23.39	3113	1.08	campesterol	[41]
16	25.66	4776	4.81	n-hentriacontane	[42]
17	27.19	1365	4.76	vanillin	[39]
18	28.81	3333	11.78	β-amirin	[43]
19	30.68	1587	3.12	spathulenol	[34]
20	32.38	1193	0.37	octyl acetate	[44]
21	36.65	3139	0.92	stigmasterol	[45]
22	37.17	3289	4.38	β-sitosterol	[45]
23	37.57	1293	2.29	germacrene D	[34,46]
24	49.57	1507	0.89	cadinene	[46]
25	55.89	1627	2.25	cadinol	[46]

GC–MS: gas chromatography–mass spectrometry; RI: retention index (RIs calculated based upon a calibration curve of a C8–C20 alkane standard mixture); RT: retention time.

The GC–MS analysis illustrates 25 compounds, constituting 82.38% of the total peak area in the H. sphondylium sample (Figure 1).

2.2. MS Analysis of H. sphondylium Sample

The mass spectrum shown in Figure 2 indicates the presence of multiple biomolecules detected and assigned to various chemical categories from terpenes, fatty acids, flavonoids, phenolic acids, amino acids, hydrocarbons, organic acids, esters, sterols, coumarins, iridoids, phenylpropanoids, alcohols, and miscellaneous constituents. These results corroborate the data reported in the literature [1,2,8,10,14,15,16,17,47,48,49,50,51].

Figure 2.

Mass spectrum of H. sphondylium sample.

Table 2 highlights the phytochemicals identified via electrospray ionization–quadrupole time-of-flight–mass spectrometry (ESI–QTOF–MS) analysis.

Table 2.

Biomolecules identified by mass spectrometry analysis in H. sphondylium sample.

No.	Detected m/z	Theoretical m/z	Molecular Formula	Tentative of Identification	Category	Ref.
1	76.07	75.07	C2H5NO2	glycine	amino acids	[47]
2	90.88	89.09	C3H7NO2	alanine	amino acids	[47]
3	106.08	105.09	C3H7NO3	serine	amino acids	[47]
4	121.13	119.12	C4H9NO3	threonine	amino acids	[47]
5	134.11	133.10	C4H7NO4	aspartic acid	amino acids	[47]
6	148.12	147.13	C5H9NO4	glutamic acid	amino acids	[47]
7	187.15	186.16	C11H6O3	angelicin	coumarins	[1]
8	193.17	192.17	C10H8O4	scopoletin	coumarins	[1]
9	203.17	202.16	C11H6O4	xanthotoxol	coumarins	[16]
10	217.21	216.19	C12H8O4	sphondin	coumarins	[16]
11	247.22	246.21	C13H10O5	isopimpinellin	coumarins	[2]
12	271.29	270.28	C16H14O4	imperatorin	coumarins	[1,48]
13	287.27	286.28	C16H14O5	heraclenin	coumarins	[1,2,48]
14	305.28	304.29	C16H16O6	heraclenol	coumarins	[1,2,48]
15	317.31	316.30	C17H16O6	byakangelicol	coumarins	[48]
16	173.25	172.26	C10H20O2	capric acid	fatty acids	[1]
17	201.33	200.32	C12H24O2	lauric acid	fatty acids	[1]
18	229.37	228.37	C14H28O2	myristic acid	fatty acids	[15]
19	255.42	254.41	C16H30O2	palmitoleic acid	fatty acids	[15]
20	257.43	256.42	C16H32O2	palmitic acid	fatty acids	[1]
21	271.49	270.50	C17H34O2	margaric acid	fatty acids	[15]
22	281.39	280.40	C18H32O2	linoleic acid	fatty acids	[1,16]
23	283.51	282.50	C18H34O2	oleic acid	fatty acids	[1]
24	284.49	284.50	C18H36O2	stearic acid	fatty acids	[1]
25	313.49	312.50	C20H40O2	arachidic acid	fatty acids	[15]
26	341.59	340.60	C22H44O2	behenic acid	fatty acids	[15]
27	271.25	270.24	C15H10O5	apigenin	flavonoids	[8,10]
28	287.23	286.24	C15H10O6	kaempferol	flavonoids	[8,10]
29	291.28	290.27	C15H14O6	catechin	flavonoids	[10]
30	303.24	302.23	C15H10O7	quercetin	flavonoids	[8,10]
31	449.41	448.40	C21H20O11	astragalin	flavonoids	[1]
32	465.39	464.40	C21H20O12	hyperoside	flavonoids	[1]
33	611.49	610.50	C27H30O16	rutin	flavonoids	[8]
34	377.35	376.36	C16H24O10	loganic acid	iridoids	[1]
35	139.11	138.12	C7H6O3	p-hydroxybenzoic acid	phenolic acids	[10]
36	155.13	154.12	C7H6O4	gentisic acid	phenolic acids	[8]
37	165.15	164.16	C9H8O3	p-coumaric acid	phenolic acids	[8,10]
38	171.11	170.12	C7H6O5	gallic acid	phenolic acids	[10]
39	181.17	180.16	C9H8O4	caffeic acid	phenolic acids	[8,10]
40	195.18	194.18	C10H10O4	ferulic acid	phenolic acids	[8,10]
41	355.32	354.31	C16H18O9	chlorogenic acid	phenolic acids	[8]
42	149.19	148.20	C10H12O	estragole	phenylpropanoids	[49]
43	401.71	400.70	C28H48O	campesterol	sterols	[15]
44	413.69	412.70	C29H48O	stigmasterol	sterols	[15]
45	415.71	414.70	C29H50O	β-sitosterol	sterols	[1,15]
46	135.23	134.22	C10H14	p-cymene	terpenoids	[14,17]
47	137.24	136.23	C10H16	α-pinene	terpenoids	[14,17]
48	151.23	150.22	C10H14O	carvone	terpenoids	[49]
49	153.22	152.23	C10H16O	phellandral	terpenoids	[49]
50	155.25	154.25	C10H18O	linalool	terpenoids	[49]
51	156.25	156.26	C10H20O	menthol	terpenoids	[49]
52	193.31	192.30	C13H20O	β-ionone	terpenoids	[49]
53	203.34	202.33	C15H22	α-curcumene	terpenoids	[17,50]
54	205.36	204.35	C15H24	germacrene D	terpenoids	[14,17]
55	207.36	206.37	C15H26	cadinene	terpenoids	[51]
56	221.34	220.35	C15H24O	spathulenol	terpenoids	[50]
57	223.38	222.37	C15H26O	cadinol	terpenoids	[51]
58	251.34	250.33	C15H22O3	xanthoxin	terpenoids	[48]
59	273.51	272.50	C20H32	β-springene	terpenoids	[50]
60	427.69	426.70	C30H50O	β-amirin	terpenoids	[48]
61	149.21	148.20	C10H12O	anethole	miscellaneous	[1]
62	151.23	150.22	C10H14O	myrtenal	miscellaneous	[17]
63	153.16	152.15	C8H8O3	vanillin	miscellaneous	[10]
64	193.22	192.21	C11H12O3	myristicin	miscellaneous	[14]
65	223.25	222.24	C12H14O4	apiole	miscellaneous	[2]
66	255.23	254.24	C15H10O4	chrysophanol	miscellaneous	[1]
67	131.22	130.23	C8H18O	n-octanol	alcohols	[14]
68	117.19	116.20	C7H16O	heptanol	alcohols	[49]
69	75.13	74.12	C4H10O	butanol	alcohols	[49]
70	103.18	102.17	C6H14O	hexanol	alcohols	[49]
71	99.15	98.14	C6H10O	hexanal	aldehydes	[14,17]
72	129.22	128.21	C8H16O	octanal	aldehydes	[17]
73	157.25	156.26	C10H20O	decanal	aldehydes	[17]
74	145.22	144.21	C8H16O2	isobutyl isobutyrate	esters	[17]
75	163.19	162.18	C10H10O2	methyl cinnamate	esters	[1]
76	173.27	172.26	C10H20O2	octyl acetate	esters	[14]
77	187.28	186.29	C11H22O2	hexyl 2-methyl butanoate	esters	[17]
78	199.31	198.30	C12H22O2	dihydrolinalyl acetate	esters	[17]
79	197.28	196.29	C12H20O2	bornyl acetate	esters	[17]
80	201.33	200.32	C12H24O2	octyl isobutyrate	esters	[14,17]
81	229.36	228.37	C14H28O2	octyl hexanoate	esters	[14]
82	219.37	218.38	C16H26	5-phenyldecane	hydrocarbons	[46]
83	261.49	260.50	C19H32	4-phenyltridecane	hydrocarbons	[46]
84	353.69	352.70	C25H52	pentacosane	hydrocarbons	[1]
85	381.69	380.70	C27H56	heptacosane	hydrocarbons	[1]
86	395.81	394.80	C28H58	octacosane	hydrocarbons	[1]
87	423.79	422.80	C30H62	triacontane	hydrocarbons	[1]
88	437.81	436.80	C31H64	n-hentriacontane	hydrocarbons	[1]

2.3. Chemical Screening

A total of 88 biomolecules identified through MS were appointed to various categories: terpenoids (17.04%), fatty acids (12.5%), coumarins (10.22%), flavonoids (7.95%), phenolic acids (7.95%), amino acids (6.81%), phytosterols (3.40%), esters (9.09%), hydrocarbons (7.95%), alcohols (4.54%), aldehydes (3.40%), phenylpropanoids (1.13%), iridoids (1.13%), and miscellaneous. Figure 3 shows the arrangement chart bar of phytochemicals from H. sphondylium according to the results of MS analysis (Table 2).

Figure 3.

Phytochemical classification bar chart of H. sphondylium sample.

2.4. Key Aroma-Active Compounds Forming Different Flavor Characteristics

The volatile organic compound (VOC) odor profile of biomolecules identified in the H. sphondylium sample is presented in Table 3 and Figure 4.

Table 3.

Volatile organic compounds identified via mass spectrometry in H. sphondylium sample.

Volatile Organic Compound	Odor Profile
p-cymene	woody
α-pinene	piney
carvone	minty
phellandral	pungent, terpenic
linalool	floral, woody
menthol	minty
β-ionone	woody
α-curcumene	herbal
germacrene D	woody
cadinene	woody
spathulenol	herbal, fruity
cadinol	herbal
xanthoxin	floral
anethole	minty
myrtenal	herbal
vanillin	vanilla
myristicin	spicy
apiole	herbal
hexanal	herbal
octyl acetate	fruity
octyl butyrate	fruity
octanal	citrus
decanal	citrus
isobutyl isobutyrate	sweet
methyl cinnamate	fruity
hexyl 2-methyl butanoate	sweet, fruity
bornyl acetate	piney
octyl hexanoate	fruity, herbal

Figure 4.

VOC odor profile compounds identified in H. sphondylium sample. VOC: volatile organic compound.

2.5. Phytocarrier Engineered System

2.5.1. FTIR Spectroscopy

Fourier-transform infrared (FTIR) spectroscopy was utilized to examine the chemical interaction between AgNPs and phytoconstituents in plants, besides the formation of the phytocarrier system. Analysis of the H. sphondylium sample (Figure 5; Table 4) revealed the presence of various categories of biomolecules, including terpenoids, fatty acids, flavonoids, coumarins, phenolic acids, amino acids, phytosterols, aldehydes, esters, iridoids, and phenylpropanoids.

Figure 5.

FTIR spectra of H. sphondylium sample and HS-Ag system. FTIR: Fourier-transform infrared; HS-Ag: H. sphondylium–silver nanoparticle system.

Table 4.

Characteristic absorption bands associated with phytoconstituents from H. sphondylium sample.

Biomolecules Category	Wavenumber [cm−1]	Ref.
terpenoids	2974, 2943, 2350, 1746, 1708, 1450, 1088, 882	[52]
coumarins	1730, 1630, 1608, 1589, 1565, 1510, 1265, 1140	[53]
flavonoids	4002–3124, 3402–3102, 1654, 1645, 1619, 1574, 1504, 1495, 1480, 1368, 1271, 1078, 768, 536	[54,55]
phenolic acids	3442, 1733, 1634, 1594, 1516, 1458, 1242, 1158, 881	[52,56]
amino acids	3400, 3332–3128, 2922, 2362, 2133, 1724–1755, 1689, 1677, 1649, 1644, 1643, 1632, 1628, 1608, 1498–1599	[52]
fatty acids	3606, 3009, 2962, 2932, 2848, 1700, 1349, 1249, 1091, 722	[36]
iridoids	1448, 1371, 1346, 1235, 1151	[57]
phytosterols	3431, 3028, 2938, 1641, 1463, 1060	[57,58]
phenylpropanoids	3188, 3002, 1636, 1504, 1449, 1248	[59]

The FTIR spectrum of the HS-Ag system exhibits the characteristic vibrational bands of the H. sphondylium sample (Figure 5). These include peaks at approximately 2922 cm⁻¹ corresponding to the asymmetric vibration of the CH₂ groups from amino acids, at ~2848 cm⁻¹ attributed to the symmetric vibration of the CH₂ groups from fatty acids, and at ~1746 cm⁻¹ attributed to the C=O stretch of terpenoids. Additionally, the spectra show a peak at ~1644 cm⁻¹ assigned to the N–H stretch of amino acids, at ~1458 cm⁻¹ attributed to the aromatic ring of phenolic acids, and at ~1242, 1060, and ~1016 cm⁻¹ associated with the C–N vibration of amines. Furthermore, peaks at ~882 and ~814 cm⁻¹ are assigned to C–O and C–H vibrations of aromatic rings, indicating the presence of AgNPs coated with sodium citrate [32].

Nonetheless, the following vibrational peaks at ~1632, 1389, 1114, and 675 cm⁻¹, characteristic of AgNPs coated with the surfactant, exhibit observable shifts to higher wavenumbers (1642, 1392, 1118, and 681 cm⁻¹) [32,60]. The spectral shifts observed indicate the interaction between AgNPs and the O–H, C=O, N–H, and C–O functional groups of the phytochemicals present in H. sphondylium sample. Notable changes in the herbal sample spectra are evident, particularly in the vibrational absorption at around 3407, 1412, and 1380 cm⁻¹ (O–H), besides 1292, 1150, and 1060 cm⁻¹ (C–O). These shifts to higher wavenumbers suggest the involvement of these functional groups in binding the AgNPs, possibly through hydrogen bonding. Furthermore, the distinct sharpening observed in the O–H and N–H stretching regions shows distinct sharpening support evidence for HS-Ag system preparation.

2.5.2. XRD Analysis

The X-ray diffraction (XRD) patterns of H. sphondylium sample and HS-Ag system are shown in Figure 6.

Figure 6.

Powder XRD patterns of H. sphondylium sample and HS-Ag system. HS-Ag: H. sphondylium–silver nanoparticle system; XRD: X-ray diffraction.

The HS-Ag system XRD pattern displays the diffraction peaks of H. sphondylium biomolecules (at 2θ: 15.78° and 22.21°) and AgNPs (at 2θ: 27.87°, 38.15°, 64.4°, and 78.5°) [32,61,62].

Notably, the distinctive peaks of phytoconstituents are shifted to lower angles, indicating the incorporation of AgNPs into the herbal matrix. The interaction between AgNPs and the herbal matrix induces structural modifications, as evidenced by the discernible shift in XRD peak positions, reflecting the influential impact of metallic NPs on the herbal matrix amorphous structure.

2.5.3. SEM and EDX Analysis

Figure 7a,b presents the scanning electron microscopy (SEM) images for the H. sphondylium sample and the HS-Ag system.

Figure 7.

SEM images of H. sphondylium sample (a) and HS-Ag system (b). HR-TEM image of AgNPs (c). HR-TEM: high-resolution transmission electron microscopy; HS-Ag: H. sphondylium–silver nanoparticle (AgNP) system; SEM: scanning electron microscopy.

The SEM image of the H. sphondylium sample (Figure 7a) revealed a complex structure comprising particles of various shapes and sizes. The HS-Ag system (Figure 7b) demonstrated a modification in the morphology of the H. sphondylium sample, with numerous nanosized spherical Ag particles (~19 nm) visibly present on the surface and within the pores of the herbal matrix particles. In the SEM image shown in Figure 7b, a few of the AgNPs from the HS-Ag system have been highlighted by encircling them in yellow to emphasize the loading of the AgNPs onto the surface and within the pores of the herbal matrix.

The morphology, shape, and dimensions of the synthesized AgNPs were thoroughly examined using high-resolution transmission electron microscopy (HR-TEM). The analysis revealed that the AgNPs exhibit a spherical morphology, with average sizes ranging from 20 to 40 nm, as depicted in Figure 7c.

Moreover, the energy-dispersive X-ray (EDX) spectra of the HS-Ag system showed characteristic peaks corresponding to both H. sphondylium sample and AgNPs, as depicted in Figure 8a,b, confirming the successful preparation of the newly engineered phytocarrier.

Figure 8.

EDX composition of H. sphondylium sample (a) and HS-Ag system (b). EDX: energy-dispersive X-ray; HS-Ag: H. sphondylium–silver nanoparticle system.

2.5.4. DLS Analysis

The study results on the stability and dynamics of herbal matrix particles, citrate-coated AgNPs and a new system obtained by the dynamic light scattering (DLS) method are shown in Figure 9a–c.

Figure 9.

DLS patterns of H. sphondylium sample (a), citrate-coated AgNPs (b) and HS-Ag system (c). DLS: dynamic light scattering; HS-Ag: H. sphondylium–silver nanoparticle (AgNP) system.

The hydrodynamic diameter of the AgNPs obtained, as determined by DLS, was measured to be 33 ± 4 nm, with a polydispersity index (PDI) of 0.15. This finding is consistent with the results from XRD and SEM, as the size determined using DLS reflects the hydrodynamic size rather than the physical size.

The DLS profile of the H. sphondylium sample and HS-Ag system displays two distinct peaks within a narrow range, indicating the presence of two particle populations for each sample. The sizes are 0.049 μm and 0.36 μm, with a PDI of 0.17 and 0.18 for the herbal matrix particles, and 0.039 μm and 0.26 μm, with a PDI of 0.26 and 0.29 for the HS-Ag system. The PDI values (PDI lower than 0.3) confirm a narrow size distribution of the NPs across all measured fractions. The observed visual stability of the suspensions is supported by the low PDI value of the samples in combination with their nanometric size.

Conversely, the narrow range of the peaks indicates high stability [63]. Additionally, the decrease in particle size in the HS-AgNPs system results in a higher surface area, leading to faster and more effective dissolution than in the H. sphondylium sample.

2.6. Total Phenolic Content and Screening of Antioxidant Potential

To comprehensively assess the antioxidant capacity, two specific in vitro assays—ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH)—were selected. In addition, the total phenolic content (TPC) assay was used to evaluate the total phenolic compounds in the herbal product and the HS-Ag system. The results are illustrated in Figure 10a–c and Table 5.

Figure 10.

Graphic representation of TPC (a), FRAP (b), and DPPH (c) assay outcomes. DPPH: 2,2-Diphenyl-1-picrylhydrazyl; FRAP: ferric reducing antioxidant power; GAE: gallic acid equivalents; HS-Ag: H. sphondylium–silver nanoparticle system; IC₅₀: half maximal inhibitory concentration; TPC: total phenolic content.

Table 5.

Antioxidant assays outcomes for both samples (H. sphondylium and HS-Ag system).

Sample	TPC [mg GAE/g]	FRAP [mM Fe2+]	DPPH IC50 [mg/mL]
H. sphondylium	8.14 ± 0.18	29.31 ± 0.11	7.65 ± 0.05
HS-Ag system	11.47 ± 0.16	32.44 ± 0.08	5.62 ± 0.07

Values are expressed as the mean ± SD (n = 3). DPPH: 2,2-Diphenyl-1-picrylhydrazyl; FRAP: ferric reducing antioxidant power; GAE: gallic acid equivalents; IC₅₀: half maximal inhibitory concentration; TPC: total phenolic content.

The findings from the TPC assay indicate a substantial rise in phenolic content (40.91%) in the HS-Ag system compared to H. sphondylium, which is attributed to the catalytic properties of AgNPs [64]. The FRAP assay data also demonstrate a moderate increase (10.67%) in reducing power for the HS-Ag system over H. sphondylium. Furthermore, the DPPH radical scavenging assay results reveal a significant decrease (26.53%) in the half maximal inhibitory concentration (IC₅₀) value for scavenging activity associated with a higher antioxidant activity.

2.7. Antimicrobial Screening

The screening of antimicrobial activity against selected pathogenic microorganisms was tested in this study, specifically against Staphylococcus aureus (Gram-positive), Bacillus subtilis (Gram-positive), Pseudomonas aeruginosa (Gram-negative), and Escherichia coli (Gram-negative), using the agar well diffusion method. H. sphondylium and a newly prepared HS-Ag system were evaluated for their antibacterial activity by measuring the diameter of inhibition zones (IZs) and comparing the results with positive (Gentamicin) and negative (dimethyl sulfoxide—DMSO) controls. The data presented in Table 6 indicate that both samples (H. sphondylium and HS-Ag system) exhibited strong antibacterial activity against all tested pathogenic microorganisms.

Table 6.

Results of antibacterial activity against selected pathogenic microorganisms.

Pathogenic Microorganism	Sample	Inhibition Zone Diameter [mm]
		Sample Concentration [μg/mL]					Positive Control (Gentamicin 100 μg/mL)	Negative Control (DMSO)
		100	125	150	175	200
Staphylococcus aureus	H. sphondylium	11.23 ± 0.75	13.98 ± 1.17	17.06 ± 0.68	21.19 ± 0.72	25.46 ± 0.45	9.57 ± 0.35	0
	citrate-coated AgNPs	13.03 ± 0.51	16.45 ± 0.55	18.85 ± 0.48	26.94 ± 0.62	30.13 ± 0.42
	HS-Ag system	14.78 ± 0.54	17.27 ± 0.78	21.62 ± 0.47	28.52 ± 0.56	34.14 ± 0.56
Bacillus subtilis	H. sphondylium	19.83 ± 0.09	21.47 ± 0.43	24.36 ± 0.32	27.69 ± 0.38	31.22 ± 0.31	17.89 ± 0.28	0
	citrate-coated AgNPs	21.32 ± 0.31	24.76 ± 0.27	26.74 ± 0.19	30.23 ± 0.22	34.58 ± 0.24
	HS-Ag system	23.11 ± 0.41	25.38 ± 0.36	29.51 ± 0.16	32.76 ± 0.47	36.25 ± 0.28
Pseudomonas aeruginosa	H. sphondylium	10.64 ± 0.27	14.09 ± 0.21	16.73 ± 0.25	18.95 ± 0.82	20.38 ± 0.17	18.67 ± 0.19	0
	citrate-coated AgNPs	9.84 ± 0.19	11.72 ± 0.23	13.81 ± 0.34	16.45 ± 0.42	18.52 ± 0.17
	HS-Ag system	21.78 ± 0.19	23.01 ± 0.17	24.74 ± 0.32	26.18 ± 0.61	27.65 ± 0.19
Escherichia coli	H. sphondylium	11.84 ± 0.37	14.69 ± 0.34	17.15 ± 0.51	19.03 ± 0.43	21.49 ± 0.34	20.69 ± 0.31	0
	citrate-coated AgNPs	13.12 ± 0.21	17.26 ± 0.27	20.07 ± 0.33	22.21 ± 0.45	25.89 ± 0.42
	HS-Ag system	20.88 ± 0.28	21.63 ± 0.25	23.06 ± 0.42	25.02 ± 0.47	27.12 ± 0.58

Values are expressed as the mean ± SD (n = 3). DMSO: Dimethyl sulfoxide; HS-Ag: H. sphondylium–silver nanoparticle (AgNP) system; SD: standard deviation.

Notably, even at the lowest concentration tested (100 μg/mL), the herbal sample, citrate-coated AgNPs and the HS-Ag system showed significantly larger IZ diameters compared to the positive control (Gentamicin) against both Gram-positive bacteria strains (S. aureus and B. subtilis). However, for the Gram-negative bacteria strains, the IZs obtained for the lowest concentration of the herbal sample (100 μg/mL) were lower than Gentamicin (18.67% against P. aeruginosa and 20.69% against E. coli). Regarding the antimicrobial activity of citrate-coated AgNPs against Gram-negative strains, it was observed that the highest concentration of AgNPs (200 μg/mL) exhibited a similar IZ diameter to Gentamicin against P. aeruginosa. In contrast, even at a concentration of 150 μg/mL, citrate-coated AgNPs showed a similar IZ diameter against E. coli. Furthermore, at higher concentrations of citrate-coated AgNPs (175 and 200 μg/mL), IZ diameters were larger than Gentamicin against E. coli. On the other hand, the HS-Ag system’s lower concentration (100 μg/mL) displayed a slightly larger IZ diameter than Gentamicin against P. aeruginosa (16.65%). Meanwhile, the antibacterial IZs against E. coli obtained for the same concentration of the HS-Ag system (100 μg/mL) were almost like Gentamicin. Finally, the highest concentrations of all samples, the herbal sample, citrate-coated AgNPs and the HS-Ag system (200 μg/mL) demonstrated the largest IZ diameters against all tested bacterial strains. Additionally, the HS-Ag system was more effective at inhibiting the growth of all tested bacterial strains at all concentrations than H. sphondylium.

To confirm the antibacterial efficacy of samples (H. sphondylium, citrate-coated AgNPs and the newly formulated HS-Ag system), the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined against all bacterial strains. The results are illustrated in Table 7.

Table 7.

MICs and MBCs of samples against selected pathogenic microorganisms.

Pathogenic Microorganism	Sample	MIC [μg/mL]	MBC [μg/mL]	Gentamicin
				MIC [μg/mL]	MBC [μg/mL]
Staphylococcus aureus	H. sphondylium	0.22 ± 0.07	0.23 ± 0.19	0.62 ± 0.22	0.62 ± 0.21
	citrate-coated AgNPs	0.14 ± 0.05	0.13 ± 0.04
	HS-Ag system	0.12 ± 0.03	0.11 ± 0.16
Bacillus subtilis	H. sphondylium	0.28 ± 0.19	0.24 ± 0.12	0.49 ± 0.18	0.43 ± 0.19
	citrate-coated AgNPs	0.18 ± 0.12	0.19 ± 0.08
	HS-Ag system	0.16 ± 0.08	0.15 ± 0.23
Pseudomonas aeruginosa	H. sphondylium	0.98 ± 0.11	0.99 ± 0.14	1.27 ± 0.16	1.26 ± 0.19
	citrate-coated AgNPs	0.67 ± 0.21	0.67 ± 0.17
	HS-Ag system	0.52 ± 0.07	0.59 ± 0.37
Escherichia coli	H. sphondylium	0.38 ± 0.09	0.31 ± 0.21	0.82 ± 0.19	0.82 ± 0.17
	citrate-coated AgNPs	0.30 ± 0.08	0.31 ± 0.11
	HS-Ag system	0.26 ± 0.13	0.26 ± 0.15

Values are expressed as the mean ± SD (n = 3). HS-Ag: H. sphondylium–silver nanoparticle (AgNP) system; MBC: minimum bactericidal concentration; MIC: minimum inhibitory concentration; SD: standard deviation.

All samples demonstrated significant antimicrobial activity in the MIC and MBC assays. The MIC value of H. sphondylium sample varied from 0.22 ± 0.07 to 0.98 ± 0.11 μg/mL, and from 0.13 ± 0.04 to 0.67 ± 0.17 μg/mL for citrate-coated AgNPs, while for the HS-Ag system, it ranged from 0.12 ± 0.03 to 0.52 ± 0.07 μg/mL. Correspondingly, the MBC values for all investigated samples aligned closely with the MIC values. These results demonstrated a superior antibacterial effect of the HS-Ag system compared to herbal and citrate-coated AgNPs samples across all bacterial strains tested. It is worth noting that the MIC and MBC values for all samples are lower than those of Gentamicin (positive control). The bacterial growth was absent in the negative control, which only contained nutrient broth.

2.8. Cell Viability Assay

Figure 11a,b illustrates the results of cell viability testing using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on H. sphondylium and HS-Ag system samples at various concentrations (75, 100, 125, 150, 175, and 200 μg/mL).

Figure 11.

Viability of NHDF and HeLa cells, 24 h after co-incubation with different concentrations of H. sphondylium sample (a) and HS-Ag system (b). Positive control wells contained untreated cells, MTT solution, and DMSO. Data are presented as mean ± SEM of three independent readings (n = 3). DMSO: Dimethyl sulfoxide; HeLa: Henrietta Lacks; HS-Ag: H. sphondylium–silver; MTT: 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NHDF: normal human dermal fibroblasts; SEM: Standard error of the mean.

The data suggest that lower concentrations of H. sphondylium correspond to higher cell viability, indicating a less toxic effect on the normal human dermal fibroblasts (NHDF) cell line. A constant, slight decrease in cell viability was observed within the 75–150 μg/mL concentration range. At higher concentrations of 175 and 200 μg/mL, a more significant decrease in cell viability occurred, but it remained above 74% (Figure 11a).

In the case of the cervical cancer (Henrietta Lacks—HeLa) cell line, there was a consistent decrease in cell viability as the concentration of the herbal extract increased. The most notable impact occurred at higher concentrations (175 and 200 μg/mL) (Figure 11b).

Similarly, in the case of the HS-Ag system, the outcomes of the MTT assay indicated that cell viability was dose-dependent. Thus, the NHDF cells displayed a continuous decrease in cell viability when the HS-Ag system concentration increased. Notably, at 200 μg/mL, the maximum concentration of the HS-Ag system corresponded to the lower cell viability value (70.46 μg/mL) but remained above the standard value (Figure 11a).

However, the HS-Ag system had a notably more pronounced negative impact on the HeLa tumor cell line, with an inversely proportional relationship between concentration and cell viability. Specifically, the maximum effect of 50.26% was observed at 200 μg/mL of the HS-Ag system (Figure 11b).

The IC₅₀ values of in vitro cytotoxicity calculated for H. sphondylium are higher than those for the HS-Ag system, as illustrated in Figure 12.

Figure 12.

In vitro cytotoxicity of HS-Ag system vs. H. sphondylium, as a function of concentration against NHDF and HeLa cell lines (after 24 h). Data are presented as mean ± SEM of three independent readings (n = 3). HeLa: Henrietta Lacks; HS-Ag: H. sphondylium–silver nanoparticle system; IC₅₀: half maximal inhibitory concentration; NHDF: normal human dermal fibroblasts; SEM: standard error of the mean.

Thus, for NHDF cells, the IC₅₀ values of H. sphondylium and the HS-Ag system were 79.82 ± 0.023 and 67.65 ± 0.019 μg/mL, respectively. For HeLa cells, the IC₅₀ values of H. sphondylium and the HS-Ag system were 61.31 ± 0.078 and 49.54 ± 0.064 μg/mL, respectively. The data suggest that the HS-Ag system exhibits higher cytotoxicity than H. sphondylium against tumor cells (19.18%).

3. Discussion

H. sphondylium, a renowned medicinal plant with well-established therapeutic properties in Romanian ethnomedicine, has gained recent attention due to its remarkable biological activity. The escalating concerns surrounding antimicrobial resistance led to a critical reevaluation of current therapeutic strategies for infectious diseases. Recent research focuses on the new selective targeting strategies for innovative antimicrobial agents. Special attention is paid to new efficient antibiotics based on medicinal plants and nanotechnology.

3.1. Screening and Classification of the Different Metabolites of H. sphondylium

Concerning the chemical composition of H. sphondylium, a total of 88 biomolecules were detected through GC–MS and ESI–QTOF–MS, encompassing a diverse array of categories, mainly terpenoids, coumarins, flavonoids, phenolic acids, amino acids, fatty acids, phytosterols, phenylpropanoids, and iridoids.

Terpenoids represent over 17% of the total H. sphondylium phytoconstituents (Figure 3). The therapeutic properties of terpenoids are multiple, including anti-inflammatory, antimicrobial, antiviral, antitumor, analgesic, cardioprotective, antispastic, antihyperglycemic, and immunomodulatory [65].

Coumarins are the third class of metabolites, representing over 10% of the phytochemicals from the hogweed sample (Figure 3). Research has reported that these secondary metabolites possess high antioxidant, antiviral, anti-inflammatory, antitumor, neuroprotective, anticoagulant, anticonvulsant, cardioprotective, antihypertensive, immunomodulatory, and antidiabetic properties [54,66].

Flavonoids, which comprise approximately 8% of the H. sphondylium sample (Table 2; Figure 3), are metabolites with outstanding biological activities: antimicrobial, antioxidant, cardioprotective, antiviral, neuroprotective, and antitumor [67].

Phenolic acids represent a significant class of phytochemicals identified in the composition of the H. sphondylium sample (Table 2; Figure 3). Research showed that these metabolites exhibit anti-inflammatory, antibacterial, antioxidant, antidiabetic, anti-allergic, antitumor, cardioprotective, and neuroprotective properties [68,69].

Amino acids are another category of phytochemicals encompassing over 83% of non-essential amino acids (glycine, alanine, serine, aspartic acid, glutamic acid) (Table 2). About 50% of these compounds (glycine, alanine, glutamic acid) exert antiproliferative and immunomodulatory activity. Over 33% (serine and threonine) act as anti-inflammatory agents. In addition, studies report the beneficial effect of aspartic acid on neurological and psychiatric diseases [70,71].

Fatty acids comprise 12.5% of total phytochemicals from the H. sphondylium sample, with about 72% saturated fatty acids (capric, stearic, behenic, lauric, myristic, margaric, arachidic, and palmitic acids), two monosaturated fatty acids (oleic and palmitoleic acids) and one ω-6 acid (linoleic acid) (Table 2). These compounds possess anti-inflammatory, antioxidant, antimicrobial, neuroprotective, and cardioprotective properties [72].

Phytosterols represent over 3% of the total phytochemicals (Table 2) and act as antioxidant, neuroprotective and cardioprotective, anti-inflammatory, antitumor, and immunomodulatory agents [73].

The phenylpropanoid estragole (Table 2) displays antibacterial, antiviral, antioxidant, anti-inflammatory, and immunomodulatory activity [74].

Iridoid compound loganic acid (Table 2) possesses neuroprotective, anti-inflammatory, antioxidant, and antiadipogenic effects [75].

3.2. New Phytocarrier System with Antioxidant, Antimicrobial and Cytotoxicity Potential

The utilization of nanotechnology and the advancement of engineered delivery systems employing metallic NPs circumvent the in vitro deficiencies, particularly stability and reduced adsorption, associated with certain phytoconstituents possessing heightened biological activity. These tailored systems promote targeted activity, prolonged drug release, reduced drug doses, and lowered toxicity. Additionally, they can improve the therapeutic effects by combining the actions of the herbal compounds and the metallic NPs [22,23,76]. As a result, a new delivery system based on AgNPs was developed from H. sphondylium.

Multiple assays provide a thorough and precise evaluation of the antioxidant potential of herbal products. In vitro tests are particularly valuable for assessing the antioxidant activity of samples containing complex compositions of biomolecules. The antioxidant activity of H. sphondylium is intricately linked to the highly active phytoconstituents.

The biological activity of AgNPs, particularly their antibacterial activity, is closely linked to the size and shape of the particles, as well as their high surface-to-volume ratio and concentration [32].

Conversely, the antioxidant potential within the HS-Ag system is derived from the phytochemicals and AgNPs conjugate effect. The results suggest that in the HS-Ag system, AgNPs, in conjunction with the phytoconstituents, could act as hydrogen donors, reducing agents, and singlet oxygen quenchers [77].

The results suggest that the antimicrobial efficacy of all samples is dose-dependent, consistent with the existing literature [32,78].

Gram-positive bacterial strains (S. aureus and B. subtilis) exhibited a greater sensitivity to both H. sphondylium, citrate-coated AgNPs and HS-Ag system samples compared to Gram-negative bacteria (P. aeruginosa and E. coli), possibly attributed to morphological variances within these distinct microorganism categories. Additionally, the outer membrane features of Gram-negative bacteria may act as a barrier against various compounds [79].

The antimicrobial activity of the H. sphondylium sample can be attributed to its complex mixture of phytoconstituents renowned for their antimicrobial properties, encompassing flavonoids, terpenoids, phenolic acids, fatty acids, and phenylpropanoids (estragole, anethole, myristicin) [80,81].

Notably, phenolic acids impact the bacterial membrane and cytoplasmic levels, while flavonoids act on the membrane level and inhibit deoxyribonucleic (DNA) and ribonucleic (RNA) synthesis [69]. Furthermore, terpenoids restrict bacterial respiration and oxidative phosphorylation [82,83].

Conversely, the antimicrobial activity of the HS-Ag system may be ascribed to the synergistic biological mechanism of phytochemicals and AgNPs. While the biological mechanism of AgNPs remains elusive, numerous studies have reported that AgNPs disrupt membrane interactions, deactivate proteins through Ag⁺ interaction and adversely impact bacterial DNA [32]. Furthermore, the antibacterial properties of AgNPs depend on other variables such as particle shape and concentration.

The lower values of the MIC and MBC are associated with the most efficient antimicrobial effect [79]. The H. sphondylium sample displayed the lowest MIC values against B. subtilis, followed by S. aureus, E. coli, and P. aeruginosa. The bacterial susceptibility diversity could be associated either with their resistance or the sample composition, specifically with the conjugate antimicrobial effect of different categories of phytoconstituents in the case of H. sphondylium, multiplied by the presence of AgNPs in the HS-Ag system [79]. Furthermore, all bacteria employed in this study are associated with various infections. Research has demonstrated that Gram-negative microorganisms are reservoirs for hospital-acquired infections, and there is a growing concern regarding drug-resistant infections attributable to Gram-negative bacteria [84]. Hence, the findings from this study advocate the potential utilization of the newly formulated HS-Ag system as an antimicrobial agent.

In vitro cytotoxicity assays are commonly employed to assess the potential toxicity of a specific compound on cell culture models. These assays ascertain the impact of the compound on cell viability, growth, morphology, and metabolism, as well as its ability to impede cell viability, cell growth, and proliferation, offering insights into its cytotoxicity as an initial step in bioavailability assessment. Among the various methods available, colorimetric assays, particularly the MTT assay, are widely utilized, considering their cost-effectiveness in vitro cell viability assessment [85,86,87]. The findings suggest that the herbal extract and the newly prepared engineered phytocarrier are not toxic to the NHDF cell line [87]. In the case of the cervical cancer (HeLa) cell line, a significant decrease in cell viability as the concentration of the herbal extract increased (175 and 200 μg/mL) was highlighted. Also, the results support the existing reported data [1]. Moreover, the HS-Ag system exhibited higher cytotoxicity than H. sphondylium against the tumor cell line. This finding could be attributed to the synergistic effects of phytoconstituents and the ability of AgNPs to facilitate the generation of reactive oxygen species (ROS) [88].

4. Materials and Methods

4.1. Chemicals and Reagents

All used reagents were of analytical grade. Ethanol, methanol, dichloromethane, chloroform, sodium carbonate, gallic acid, DPPH, acetate buffer solution (pH 4–7), FRAP assay kit (MAK369-1KT), and DMSO were acquired from Sigma Aldrich (München, Germany) and used without further purification. The MTT kit was obtained from AAT Bioquest (Pleasanton, CA, USA). Ultrapure water was used in all experiments.

4.2. Cell Lines

NHDF and HeLa cell lines were purchased from the American Type Culture Collection (ATCC; Manassas, VA, USA). Both cell lines were cultivated at 37 °C, in Dulbecco’s Modified Eagle’s Medium (DMEM; Gibco, Life Technologies, Leicestershire, UK), supplemented with 10% fetal bovine serum (FBS), and 1% antibiotic antimycotic solution (Sigma Aldrich).

4.3. Bacterial Strains

S. aureus (ATCC 29213), B. subtilis (ATCC 9372), P. aeruginosa (ATCC 27853), and E. coli (ATCC 25922) were purchased from the ATCC (Manassas, VA, USA).

4.4. Plant Material

The H. sphondylium samples (whole plant—stems of 165 cm in height, leaves, flowers of 25 cm diameter, and roots) were collected in June 2022 from the area of Timiş County, in Western Romania (geographic coordinates 45°43′02″ N, 21°19′31″ E) and taxonomically authenticated at the West University of Timişoara. Voucher specimens (HERA-SPD-2022-0806) were deposited at the Department of Pharmaceutical Botany, Faculty of Pharmacy, University of Medicine and Pharmacy of Craiova, Romania.

4.5. Preparation of AgNPs

AgNPs were prepared according to a procedure described in our previous paper [32].

4.6. Plant Sample Preparation for Chemical Screening

The freeze-dried plant samples (whole plant) were milled using a planetary Fritsch Pulverisette mill (Idar-Oberstein, Germany), at 720 rpm for 12 min at 24 °C, and then sieved through American Society for Testing Materials (ASTM) standard test sieve series to obtain particles of 0.25–0.30 mm range. The vegetal material was subjected to sonication extraction (Elmasonic, Singen, Germany) for 50 min at 45 °C and 65 Hz and dissolved in methanol (20 mL). All extracts were prepared in triplicate.

4.7. GC–MS Analysis

GC analysis was performed using the GCMS-QP2020NX Shimadzu equipment (Kyoto, Japan) provided with a ZB-5MS capillary column (30 m length, 0.25 mm inner diameter, 0.25 μm film thickness) from Agilent Technologies (Santa Clara, CA, USA). Helium was used as the carrier gas at a flow rate of 1 mL/min.

4.7.1. GC–MS Separation

The oven temperature program was initiated at 50 °C, held for 2 min, and subsequently ascended to 300 °C at a rate of 5 °C per minute, where it was maintained for 4 min. The injector’s temperature was registered at 280 °C, while the interface temperature at 225 °C. Compound mass was measured at an ionization energy of 70 eV, commencing after a 2 min solvent delay. The mass spectrometer source and MS Quad were maintained at 225 °C and 160 °C, respectively. The compounds’ identification was accomplished based on their mass spectra, compared with the USA National Institute of Standards and Technology (NIST) 2.0 software (NIST, Gaithersburg, MD, USA) database, and supplemented with a literature review.

4.7.2. Mass Spectrometry

The MS experiments were carried out using an ESI–QTOF–MS analysis system (Bruker Daltonics, Bremen, Germany). The mass spectra were acquired in the positive ion mode over a mass range of 100 to 3000 m/z, with a scan speed of 2.0 scans per second, a collision energy ranging from 25 to 85 eV, and a source block temperature set at 85 °C. The identification of phytoconstituents relied on the standard library NIST/National Bureau of Standards (NBS)-3 (NIST, Gaithersburg, MD, USA) and was supplemented with a literature review. The obtained mass spectra values and the identified secondary metabolites are shown in Table 2.

4.8. Phytocarrier System Preparation (HS-Ag System)

The HS-Ag system was prepared by mixing H. sphondylium (solid herb samples prepared as previously described) with an AgNPs solution in a 1:3 mass ratio. The obtained mixture was subjected to ultrasonic mixing for 20 min at 40 °C, and then filtered (F185 mm filter paper) and dried in an oven at 40 °C for 6 h. Each experiment was carried out in triplicate.

4.9. Characterization of HS-Ag System

4.9.1. FTIR Spectroscopy

Data collection was conducted after 30 recordings at a resolution of 4 cm^–1, in the range of 4000–400 cm^–1, on Shimadzu AIM-9000 spectrometer with attenuated total reflectance (ATR) devices (Shimadzu, Tokyo, Japan). The assignment of wavelengths was based on a literature review.

4.9.2. XRD Spectroscopy

The X-ray powder diffraction (XRD) was carried out on a Bruker AXS D8-Advance X-ray diffractometer (Bruker AXS GmbH, Karlsruhe, Germany), CuKα radiation, k 0.1541 nm, equipped with a rotating sample stage, Anton Paar TTK low-temperature cell (−180 °C to 450 °C), high-vacuum, inert atmosphere, and relative humidity control, Anton Paar TTK high-temperature cell (up to 1600 °C). The XRD patterns were compared with those from the International Centre for Diffraction Data (ICDD) Powder Diffraction Database (ICDD file 04-015-9120). The average crystallite size and the phase content were determined using the whole-pattern profile-fitting (WPPF) method.

4.9.3. SEM Analysis

SEM micrographs were captured utilizing an SEM–energy-dispersive X-ray spectroscopy (EDS) system (Quanta Inspect F50; FEI-Philips, Eindhoven, The Netherlands) equipped with a field-emission gun (FEG), providing a resolution of 1.2 nm. Additionally, the system incorporates an EDX spectrometer, with an MnK resolution of 133 eV.

4.9.4. DLS Particle Size Distribution Analysis

DLS analysis was conducted on a Microtrac/Nanotrac 252 (Montgomeryville, PA, USA). Each sample was analyzed in triplicate at room temperature (22 °C) at a scattering angle of 172°.

4.10. Assessment of the Total Phenolic Content and Antioxidant Activity

The assessment of the total phenolic compounds in the herbal product and the HS-Ag system was carried out by TPC (Folin–Ciocalteu assay). The antioxidant activity of the H. sphondylium sample and of the HS-Ag system was evaluated using two different methods: FRAP and DPPH. All experiments for antioxidant activity screening were performed in triplicate.

4.10.1. Sample Preparation

Separately, 0.22 g of the H. sphondylium sample and 0.22 g of the HS-Ag system were added to 6 mL of 70% ethanol. Following a 10 h stirring period at room temperature (23 °C), the mixtures were centrifuged at 5000 rpm for 8 min. The resulting supernatant was collected for further evaluation of the antioxidant potential of each sample.

4.10.2. Determination of TPC

The TPC of the H. sphondylium and HS-Ag system samples prepared as stated above (vide supra) was determined spectrophotometrically (FLUOstar Optima UV-Vis spectrometer; BMG Labtech, Offenburg, Germany) according to the Folin–Ciocalteu procedure adapted from our earlier publication [64]. The results were expressed in gallic acid equivalents (mg GAE/g sample). Sample concentrations were calculated based on the linear Equation (1) obtained from the standard curve and the correlation coefficient (R² = 0.9997):

y = 0.0021x + 0.1634 (1)

4.10.3. FRAP Assay

The FRAP antioxidant activity of the H. sphondylium and HS-Ag system samples was determined spectrophotometrically (FLUOstar Optima UV-Vis spectrometer; BMG Labtech) at 595 nm, using a FRAP Assay Kit, according to the procedure described in our earlier publication [36]. The results were expressed in mM Fe²⁺, calculated according to Equation (2):

$$FRAP={\displaystyle \frac{mM{Fe}^{2+}\times F_D}{V}}$$ (2)

where FRAP: ferric reducing antioxidant power; mMFe²⁺: iron ions (Fe²⁺) amount generated from the calibration curve of each sample (mM); F_D: dilution factor; V: volume of each sample (μL).

4.10.4. DPPH Radical Scavenging Assay

The DPPH radical scavenging activity of the H. sphondylium and HS-Ag system samples was performed according to the procedure described in our earlier publication [64]. The absorbance (A) was recorded at 520 nm (FLUOstar Optima UV-Vis spectrometer; BMG Labtech). The IC₅₀ values (μg/mL) were determined from the inhibition percentage, Inh(%), from the calibration curve generated for each sample, according to Equation (3):

$$Inh(\%)={\displaystyle \frac{(A_0-A_1)}{A_0}}\times 10$$ (3)

4.11. Antimicrobial Test

Agar well diffusion assay, MICs, and MBCs were conducted to evaluate the antimicrobial activity of H. sphondylium and HS-Ag system.

MICs and MBCs were determined using the microbroth dilution method (Mueller–Hinton medium). MIC was considered the lowest compound concentration that inhibits bacterial growth, while MBC represents the lowest concentration at which no visible bacterial growth occurs after 14 h incubation. The microorganism growth inhibition was evaluated as the optical density at 600 nm using a T90+ UV–Vis spectrophotometer (PG Instruments, Lutterworth, UK) [89].

Nutrient agar and nutrient broth were prepared according to the manufacturer’s instructions and autoclaved at 120 °C for 20 min. The final concentration of microorganisms was adjusted to 0.5 McFarland Standard (1.5 × 10⁸ CFU/mL; CFU: Colony-forming unit). Each assay was performed in triplicate [89].

The diluted sections of five concentrations (100, 125, 150, 175, and 200 μg/mL) were prepared using 25% DMSO [89].

The antimicrobial potential of H. sphondylium and the HS-Ag system was evaluated using the agar well diffusion method according to the experimental procedure adapted from the literature [79,90,91].

The bacterial strains were initially cultured on a nutrient substrate and then inoculated for 24 h. Circular wells were created using a sterile glass capillary (5 mm). The bacterial strains (4–6 h) were streaked onto the nutrient agar using a sterile swab, and this process was repeated three times, with the plate rotated between each streaking. Next, 1 mL from each sample (H. sphondylium and HS-Ag system) concentration was introduced into the designated wells. The plates were then placed in an incubator at 37 °C for 24 h and later analyzed to determine the IZs. DMSO served as the negative control, while Gentamicin (100 μg/mL) was used as the positive control. The diameter (mm) of the IZs around the discs was measured using a ruler to determine the extent of bacterial growth inhibition. Each assay was performed in triplicate [79,90,91].

4.12. Cell Culture Procedure

4.12.1. Cell Culture and Treatment

The cell lines utilized in this study included NHDF and HeLa cells (ATCC; Manassas, VA, USA). The cells were cultured at 37 °C under 5% carbon dioxide (CO₂) and 100% humidity in DMEM supplemented with FBS and 1% antibiotic antimycotic solution. After seeding the cells at a density of 4 × 10³ cells/well in 96-well plates, they were allowed to reach 90% confluency over 24 h. Subsequently, the culture medium was replaced with a fresh medium containing varying concentrations (75, 100, 125, 150, 175, and 200 μg/mL) of H. sphondylium and the HS-Ag system. The cells were then cultured for an additional 24 h. A control group with fresh standard medium and positive and negative controls was included in the 96-well culture plate (eight wells for each test material). The experiments were conducted in triplicate, and cell viability was assessed following 24 h of incubation at 37 °C under 5% CO₂.

4.12.2. MTT Assay

The test materials were aspirated from each well of the initial plate. Subsequently, 25 μL of MTT reagent was pipetted into each well and incubated for 2 h at 37 °C in a CO₂ incubator. Subsequently, the formazan crystals formed were solubilized using DMSO. The absorbance of the samples was then quantified at a wavelength of 540 nm using a Multi-Mode Microplate Reader Synergy HTX spectrophotometer (Agilent Technologies, Santa Clara, CA, USA). Finally, the cell viability was calculated according to Equation (4):

$$CV(\%)={\displaystyle \frac{{OD}_{sample}-{OD}_{blank}}{{OD}_{control}-{OD}_{blank}}}\times 100$$ (4)

where CV(%): cell viability; OD: optical density of the wells containing cells with the evaluated sample (OD_sample), only cells (OD_control), and cell culture media without cells (OD_blank).

As per the producer’s specifications, the positive control consists of untreated cells, MTT solution, and DMSO, while the negative control consists of only dead cells, MTT solution, and DMSO. The IC₅₀ values denote the concentrations (75, 100, 125, 150, 175, and 200 μg/mL) at which both samples (H. sphondylium and HS-Ag system) displayed 50% cell viability for NHDF and HeLa cell lines. The cell viability data were plotted on a graph, and the IC₅₀ values were subsequently calculated [92].

4.13. Statistical Analysis

All experiments were performed in triplicate for all samples, all calibration curves, and concentrations. Statistical analysis was carried out using Student’s t-test and expressed as mean ± standard deviation (SD) using Microsoft Office Excel 2019 (Microsoft Corporation, Redmond, WA, USA). Dunnett’s multiple comparison post hoc test following a one-way analysis of variance test (ANOVA) was used to analyze the results. p-values <0.05 were considered statistically significant.

5. Conclusions

This study discusses the development of a novel plant-based system using AgNPs. FTIR, SEM, XRD, and DLS findings confirmed the successful incorporation of AgNPs into herbal matrix (H. sphondylium) particles and pores, resulting in the preparation of the HS-Ag system. Additionally, the antioxidant screening, antimicrobial, and in vitro cell viability investigations demonstrated that this innovative system exhibits enhanced biological properties compared to H. sphondylium. Collectively, this research work suggests that this new phytocarrier (HS-Ag system) holds promise for a wide range of medical applications.

Author Contributions

Conceptualization, A.-E.S., L.E.B. and C.B.; methodology, A.-E.S., G.B. and C.B.; validation, A.-E.S., L.E.B., G.D.M., D.-D.H. and C.B.; investigation, A.-E.S., G.V., T.V., G.D.M., G.B., D.-D.H., M.V.C. and C.B.; resources, A.-E.S.; writing—original draft preparation, A.-E.S., L.E.B. and G.D.M.; writing—review and editing, A.-E.S., L.E.B. and G.D.M.; supervision, A.-E.S., L.E.B. and C.B. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original data presented in the study are openly available in [GoFile repository] at [https://gofile.me/7rkqY/KHgZHOglD, accessed on 20 August 2024].

Conflicts of Interest

The authors declare no conflicts of interest.

Funding Statement

This work was supported by a grant from the European Research Executive Agency, Topic: HORIZON-MSCA-2022-SE-01-01, Type of action: HORIZON TMA MSCA Staff Exchanges, Project: 101131420—Exploiting the multifunctional properties of polyphenols: from wastes to high value products, Acronym: PHENOCYCLES.