Exploring the pharmacological and chemical aspects of pyrrolo-quinazoline derivatives in Adhatoda vasica

Abstract

Adhatoda or Justicia is one of the biggest and complex genera of the Acanthaceae family. Adhatoda vasica is commonly known as ‘Adosa’. It is an ayurvedic medicine with a medicinal history of more than a thousand years in India. Traditionally, it is used to treat cough, asthma, phlegm, bleeding hemorrhoids, for both adults and youth. This plant possesses antiarthritis, antiseptic, antimicrobial, anti-tuberculosis, anti-inflammatory and abortifacient properties. Alkaloids are the major phytoconstituents present in the plant in the form of pyrrolo-quinazoline derivatives viz vasicine, vasicinone, vasicinol, adhatodine, adhatodinine, adhavasinone and anisotine etc. The asserted objectives are to conduct a systematic review on the phytochemistry, pharmacology and traditional uses of A. vasica, as well as highlighting the challenges found in the research. This will promote the utilization of A. vasica at extract level and further development of new drug leads based on the compounds isolated and used for treatment of various ailments. The present review covers the literature survey from 1888 to 2023. The relevant data has been collected from various peer-reviwed journals, and books via Sci-Finder, PubMed, Science Direct, Google Scholar, EBSCO, online electronic journals, SpringerLink and Wiley. This paper aims to present a systematic review of known traditional applications, pharmacological and chemical aspects in Adhatoda vasica.

1. Introduction

Acanthaceae are the ninth largest pantropical family of dicotyledonous plants, including over 200 genera and 2000 species [1]. Adhatoda or Justicia is the one of the biggest genera of Acanthaceae family. This genera is an important source of therapeutic drugs and its species are distributed in all continents, mainly in tropical and subtropical regions. In America, only three species viz Justicia spicigera, Justicia secunda and Justicia pectoralis are most widely used for medicinal purposes, but very few studies related to their chemical composition and pharmacological properties have been done yet. Asian species Justicia adhatoda, Justicia beddomei and Justicia adhatoda are most promising species of this genus [2]. Justicia adhatoda is also known as Adhatoda vasica. Adhatoda vasica (L.) Nees (Fig. 1) is commonly known as ‘Vasaka’ in Ayurveda and ‘Malabar nut'in English. It is a very small, evergreen shrub that is geographically distributed throughout India up to altitude of 1300 m and mainly found in sub-Himalayan areas. It is also distributed in Nepal, Pakistan, Myanmar and Germany. The plant not only been used in the indigenous system of medicine in India since thousands of years [3], but also a well-known drug in Ayurvedic and Unani medicine [4]. It is used as traditional Indian medicine for treating bronchitis, tuberculosis, other lung and bronchiole disorders. This plant is included in the “Manual of Traditional Medicine in Primary Health Care”, published by the World Health Organization, as it has been traditionally used for treating young and old people suffering from cough, asthma, breathing trouble, phlegm, allergic conditions, bleeding hemorrhoids [5]. Several herbal remedies containing A. vasica are commercially available viz Kada [6]; Femiforte [7]; Salus Tuss [8]; Kan Jang, Spirote [1,9]. Adusa is well known for anthelmintic and weedicide properties [10]. Alkaloids like pyrrolo-quinazoline derivatives are the main classes of secondary metabolites that have been isolated from Adhatoda [11]. All findings about the pyrrolo-quinazoline derivatives and other phyto-constituents indicate that Adhatoda is an important genus of the Acanthaceae family having a commercial reputation and can be encouraged for diversified applications like medicinal and other potential uses [12].

Fig. 1.

Adhatoda vasica plant: (a) Whole aerial part (b) Flowering twig.

(These photographs were taken from Gasiyaar near Iswal, Udaipur).

Research data on Adhatoda vasica was collected from Sci-Finder, PubMed, ScienceDirect, Google Scholar, EBSCO, online electronic journals, SpringerLink and Wiley and is shown in the form of the bar graph. This graph clearly indicates that it is an ancient plant being studied since 1925 and is being studied largely which is clear from the number of increasing publications in the recent years (Fig. 2).

Fig. 2.

The number of publications published on Adhatoda vasica and its medicinal applications since 1925.

Earlier reviews of Adhatoda vasica have incorporated its pharmacological activities [[13], [14], [15], [16], [17], [18], [19], [20], [21]], phytochemistry [[22], [23], [24], [25], [26], [27], [28], [29]] and ethnomedicinal uses [[30], [31], [32], [33]]. In this paper, we have discussed the bioactivities confirming the ethnopharmacological uses of Adhatoda vasica and its potential for further investigation, exploitation, and utilization.

2. Ethnomedicinal uses

Adhatoda vasica has been used in indigenous medicine to treat a number of ailments, including colds, coughs, asthma, whooping cough, leprosy, chronic bronchitis, heart problems, blood disorders, fever, vomiting, thirst and memory loss [[33], [34], [35], [36]]. An ammonical vapour is formed when leaves are smoked in a pipe, which aids in breathing for asthma patients [14]. In Ayurveda, due to its properties like Tikta-Kashaya rasa, katu vipaka and sheeta virya, it is known for its use to cure diseases like Gulma, Raktapitta, Swasa-kasa etc. [37]. The herbal basak tea prepared from its leaves can be developed as a good expectorant for the treatment of asthma [38].

A decoction of leaves boiled in water is utilized to alleviate rheumatic pain and urinary tract infections [39]. In Ayurveda, leaves of Adhatoda vasica is an important drug, used as an expectorant [4]. Vasicine helps in condensing sputum and is therefore the vital component for throwing sputum out of the body [15]. Quinazoline alkaloids are active principles for this property. Traditionally, leaves’ juice (swarasa) is obtained by subjecting a bolus of crushed fresh leaves to heat followed by squeezing out the juice [40,41]. Leaves extract is used to stimulate uterine contractions, thus speeding child birth in various parts of India [2]. A survey revealed that 70 % of the pregnant women had been previously using the leaves of A. vasica orally to induce abortion in Gora village, Lucknow [42]. This observation has been earlier mentioned by scientists from the same institute in a report on the abortifacient activity of A. vasica in rats [43]. There is one indication of use of the roots for facilitating the expulsion of foetus or helping parturition [[44], [45], [46]]. The route of administration is probably a local application as mentioned in one of references [45].

Ethno-medicinal uses of A. vasica have been described in Table 1.

Table 1.

Ethnomedicinal uses of plant parts of A. vasica.

Plant part/s	Disease	Mode of administration	References
Leaves	Malaria	Leaves paste applied to body and left for 24 h, to cure chronic malaria	[47]
	Whooping cough and asthma	Leaves juice administered orally	[48]
		Leaves decoction with honey taken thrice a day	[49]
		Inhalation of smoke obtained from burning dry leaves by patients suffering from asthma, chronic bronchitis	[50]
	Diabetes	Leaves juice of A. vasica and Andrographis paniculata given together for 21 days	[51]
		Chewing of young leaves empty stomach to cure diabetes	[52]
	Poisonous bites	Leaves paste applied externally and leaves juice taken internally as an antidote	[53]
	Fits	Juice of leaves of A. vasica along with Piper nigrum, Zingiber officinalis and beetle leaf given to cure epilepsy	[54]
	Ear pain	Leaves decoction is used	[55]
	Inflammation	Leaves applied externally as poultice	[56]
	Arthritis	Two tea spoons of leaves extract taken twice a day	[55]
	As antiseptic lotion	Leaves decoction is used	[55]
	Scabies	Use of leaves decoction	[55]
	Rheumatism	Leaves paste applied externally	[57]
	Jaundice	Two spoons of leaves extract with sugar taken twice a day for a month.	[58]
	Eczema, cuts and wounds.	Leaves paste applied externally.	[48]
	Diarrhoea and dysentery	Leaves extract used	[57]
	Sprains	Leaves paste applied externally	[59]
Roots	Snake bite	Roots and Leaves decoction of A. vasica mixed with the extracts of Alangium salvifolium and Coccinia grandis given orally as an antidote	[60]
	Gonorrhoea	Roots extract used as anti gonorrhoeal agent	[61]
	Leucorrhoea and gynaecological problems	Roots bark juice given along with honey	[62]
	Labour pains	Application of roots paste on the abdomen and vagina at the time of child birth.	[59]
	Rheumatism	Roots extract applied externally	[57]
	Dysentery	Fresh roots extract taken	[63]
	Asthma	Root bark decoction taken along with honey	[64]
Flowers	Asthma	Floral extract mixed with Solanum surattense and given	[65]
	Ophthalmia	Fresh flowers extract used	[66]
	Jaundice	Flowers extract given	[65]
	Diabetes	Flowers along with powdered neem leaves and gum of Acacia nilotica given to patients having diabetes.	[65]
	Muscular spasms	Flowers and fruits extract taken to cure spasms.	[61]
	Pimples	Application of floral extract along with mustard oil	[65]
	Tuberculosis	Flowers and raw roots chewed empty stomach once a day	[51]
Whole plant	Asthma, bronchitis, Cough and cold	Whole plant extract used	[66]
	Liver fever	Whole plant extract used to cure liver fever	[67]
	Jaundice	Decoction of whole plant taken	[68]
	Scabies	Extract of whole plant used	[69]
Stem/Bark	Stomach pain	Extract given	[70]
	Nausea	Bark and young leaves juice taken as anti- emetic tonic	[71]
	Intestinal worms	Bark and young leaves juice given to kill intestinal worms	[71]

Folks and tribes have been using A. vasica to cure ailments and diseases, thus, it would be interesting to explore inception time of usage the plant for medicinal purposes to have better understanding of significance of A. vasica.

3. Pharmacology

Over the past decades, numerous researchers have investigated the pharmacological activities of A. vasica. Summary of the pharmacological properties is given in Table 2.

Table 2.

Brief summary of the pharmacological properties.

S. No	Pharmacological activities	Parts/extracts/possible chemical constituents	Effective dose range	Test system for activity	Result	References
1	Antibacterial/Antimycobacterial activity	Leaves: crude alkaloids, petroleum ether extract, alcohol extract and hot water extract	–	Bacillus cereus, Bacillus subtilis, Bacillus-megaterium, Saimoneiia typhi, Staphylococcus aureus, Vibrio cholerae, E. coli	Mild inhibition against subject microrganisms in different degrees was found.	[72]
		Vasicine, vasicinone, vasicine acetate, 2-acetyl benzyl amine, vasicinolone Vasicine acetate and 2-acetyl benzylamine isolated from hexane extract	10–150 μg/mL 200 and 50 μg/mL	E. coli Mycobacterium tuberculosis	Vasicine at 20 μg/mL exhibited potent antibacterial activity against E. coli. Significantly inhibited M. tuberculosis as well as one multidrug resistant (MDR) strain and one susceptible strain.	[73] [74,75]
		Vasicine acetate	125 μg/mL	E. aerogenes, S. epidermidis, P. aeruginosa, M. luteus	Vasicine acetate exhibited good zone of inhibition against tested bacteria.	[72]
		Phytol	2, 5 and 8 mg/kg	Bacillus licheniformis PKBMS16 injected experimentally challenged ornamental goldfish Carassius auratus	Phytol treated group significantly (P < 0.01 & P < 0.05) reduced the rate of fish mortality, thus supporting its potential as a new compound for inducing fish immunity.	[76]
		Leaves extract	–	Gram positive and gram-negative bacteria	Gram-positive bacteria had the highest antibacterial activity.	[77]
		Leaves extract	–	P. aeruginosa, S. aureus, S. pyogenus, E. coli	Largest zone of inhibition was found against P. aeruginosa.	[78]
2.	Antiallergic and anti-asthmatic activity	In vivo: Ethanolic extract of plant	250, 500, 750 mg/kg	Acetylcholine and histamine induced brancho-spasm in guinea pigs	Spasmolytic effect of ethanolic extract of A. vasica found similar to ketotifen (1 mg/kg).	[79]
		In vitro: Ethanolic extract of plant	250, 500, 750 μg/mL	Isolated guinea pig ileum	Significant increase in the contractions to histamine and acetylcholine was observed.	[79]
		Plant: Aqueous extract	130 mg/kg	Ova-allergen mouse model	Extract attenuated the increased airway resistance and inflammation in acute allergic asthmatic mice.	[80]
3.	Radioprotective effects	Leaves: ethanolic extract	800 mg/kg	Swiss albino mice exposed to 8 Gy radiation	Significant prevention in chromosomal damage in bone marrow cells of radiation-induced mice.	[81]
4.	Antimutagenic activity	Whole plant extract	50 and 100 mg/kg by weight	Swiss albino mice toxicated with CdCl2 (5 mg/kg by weight)	Significant decrease in malanodialdehyde formation and xanthine oxidase levels was observed.	[82]
5.	Anti-tubercular activity	Volatile extract from leaves	340 mg/kg	Parkes albino mice infected intravenously with the Ravenel Rv strain of M. tuberculosis	Volatile principle showed no anti-tubercular properties in mice on oral administration.	[83]
		Ambroxol and bromhexine (semi synthetic derivatives of vasicine)	50 mg/L for ambroxol and 6 mg/L for bromhexine	Against M. tuberculosis in vitro	Ambroxol and bromhexine showed pH-dependent growth-inhibitory effect on M. tuberculosis.	[84]
6.	Anti-ulcer activity	Leaves powder	500 mg/kg in 0.2 % agar	Ethanol induced and Pylorus ligation plus aspirin-induced rats	The ethanol-induced ulceration model had the highest level of activity (80 %).	[85]
7.	Allelopathic activity	Fresh and dried aqueous extract of leaves	60 % concentration of extract	Seeds of Capsicum annum L.	Dry aqueous extract was found more phytotoxic than fresh aqueous extract.	[86]
8.	Antifeedant and toxic activity	Leaves: Methanolic extract	200–1000 ppm	Spodoptera littoralis larvae	Crude extract lowered growth, consumption, utilization of swallowed and digested food, and approximate digestibility substantially.	[87]
9.	Sucrase inhibitory activity	Leaves: Methanolic extract, vasicine, vasicinol	–	Screening experiment for rat intestinal α -glucosidase	IC50 values were 125 μM and 250 μM for vasicine and vasicinol respectively.	[88]
10.	Anti-inflammatory activity	Vasicine	0.2 mg/kg body weight	Wistar strain of albino rats with induced lung damage	Decrease in lipid peroxidase and increase in antioxidants catalase, superoxide dismutase, glutathione peroxidase was observed.	[89]
		Methanol extract, saponins and alkaloids, non-alkaloid fraction	50 μg/pellet	Hen's egg (Chorioallantoic membrane test)	Potent anti-inflammatory activity was shown by the alkaloid fraction at a dose of 50 μg/pellet whereas less activity was shown by MeOH and the other fractions.	[90]
		Vasicine, vasicinone, vasicine acetate, 2-acetyl benzyl amine, vasicinolone	20 mg/kg for vasicine and 10 mg/kg for vasicinone	Carragenan and CFA-model induced paw oedema.	Most potent anti-inflammatory effects by vasicine and maximum inhibition rate was observed for vasicinone.	[73]
		Methanolic extract of leaves	200,400,600 mg/kg	Carrageenan-induced paw Oedema in wistar albino rats	400 mg/kg dose showed significant inhibition of carrageenan-induced inflammation.	[91]
11.	Abortifacient activity	Leaves: aqueous extract	175 mg/kg	Female albino rats	100 % abortifacient activity was observed.	[92]
		Vasicine	2.5–10 mg/kg	Hamsters, rabbits, rats and guinea pigs	Uterotonic and abortifacient effects shown by vasicine probably by enhancing the release and synthesis of prostaglandins.	[93]
12.	Antiviral activity	Methanolic and aqueous extracts of whole plant	10 mg/mL	Influenza virus	100 % and 33 % Reduction in hemagglutination by methanolic and aqueous extract respectively.	[94]
13.	Hypoglycemic activity	Ethanolic extract of the leaves	–	Rats	–	[95]
		Non nitrogenous principle from leaves	–	Rabbits	Lowering of blood sugar level was observed.	[3,96]
14.	Anticholinesterase activity	Root/Vasicinol	–	Cats, guinea pigs	Contraction of the isolated gut and depression of the isolated heart were noted in guinea pigs, as well as hypotension in cats.	[97]
15.	Cardioprotective activity	Vasicine and vasicinone	–	–	Significant reduction in cardial depressant effects by vasicine, whereas no effect by vasicinone was observed.	[3]
16.	Thrombolytic activity	Root extract	5 mg/mL NaCl solution	In vitro thrombolytic model	Adhatoda showed 19.63 % clot lysis activity.	[98]
17.	Wound-healing activity	Methanolic, chloroform and diethyl ether extracts	10 % w/w	Excision wound model in albino rats	98.50, 87.46, 80.65 and 68.70 % wound contraction observed for nitrofurazone, methanolic, chloroform and diethyl ether extract treated groups respectively.	[99]
		Chloroform and alcoholic extracts of leaves	–	Male buffalo calves	Increase in tensile strength, breaking strength, collagen, elastin, hydroxyproline etc. were observed.	[100,101]
18.	Anti-tussive activity	Vasicinone and vasicine	–	Unanaesthetized guinea pigs and anaesthetized guinea pigs and rabbits	Action found similar to codeine.	[102]
19.	Hepatoprotective activity	Leaves: aqueous extract	50–100 mg/kg	d-galactosamine liver damage induced in rats	Results supported the use of the plant as hepatoprotective element in traditional medicine.	[103]
		Vasicinone	25 mg/kg/day for 7 days	CCl4 induced acute hepatotoxicity model in mice	Normal hepatic cords and absence of necrotic changes suggested recovery from CCl4 induced liver damage in rats.	[104]
20.	Anti pyorrhoeal activity	Leaves extract massaged on the inflamed gums	Application twice a day for three weeks.	Patients with pyorrhoea complain	Reduction and relief in the inflammatory and bleeding conditions of gums was observed.	[105]
21.	Anticancer activity	Whole plant	Prophylaxis dose (50 and 100 mg/kg BW)	Ferric nitrilotriacetate (Fe-NTA)–induced renal oxidative stress and tumor promotion in rats	Results showed that A. vasica can reduce hyperproliferative response toxicity and carcinogenic activity of Fe-NTA.	[106]
		Leaves extract	10,50,100 μg/mL	Human lung epithelial adenocarcinoma cell line (HCC- 827) using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay	Methanolic extract showed cytotoxic effect on the cancerous cells which increased with the increase in dose of the extract.	[107]
		Ethanolic extract	–	In-vitro studies on Hela, HepG2, MCF-7, MDAMB-231 cell lines with normal cells as positive control	Ethanolic extract showed good cytotoxic activity (60 %, 60 %, 85 % and 65 %) on Hela, HepG2, MCF-7, MDAMB-231 cell lines respectively.	[108]
		Vasicine acetate	2000, 1000, 500, 250, 125, and 62.5 μg/mL	A549 human adenocarcinoma cancer cell line using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay	Vasicine acetate showed prominent in vitro cytotoxic activity against A549 lung adenocarcinoma cancer cell line.	[109]
		2-acetyl benzyl amine	0.42 mM	NB-4, MOLM-14, CEM, Jurkat, K562, IM-9, and HL-60	2-Acetyl-benzylamine was shown to be cytotoxic to MOLM-14 and NB-4 cells, with IC50 values of 0.40 and 0.39 mM, respectively.	[110]
22.	Radioprotective effect	Ethanolic extract of the leaves	800 mg/kg body weight	Swiss albino mice exposed to 8.0 Gy radiation	Pretreatment with A. vasica leaf extract resulted in a considerable rise in GSH content and a decrease in LPO level in irradiated animals.	[81,111]
23.	Immuno-stimulant activity	Ethanolic extract of the leaves	500 mg/kg	Swiss albino mice	Protection against E. coli induced abdominal peritonitis, increase in blood lymphocytes, total WBC, splenic lymphocytes and peritoneal macrophages was observed.	[112]
		Methanolic extract of plant	200 mg/kg	Mice	Increase in the WBC count to 16 % and significant protective effect against cyclophosphamide induced myelosuppression upto 80 % were observed.	[113]
24.	HIV-Protease inhibitor activity	Crude extract of whole plant	–	Pepsin assay	A. Vasica exhibited pot inhibitory activity of enzyme Pepsin.	[114]
25.	Anti-typhoid activity	Leaves: methanolic extract	2.50 mg/mL	Salmonella typhi	Methanolic extract proved effective against Salmonella typhi as an antityphoid agent.	[115]
26.	Renal protective activity	Leaves: ethanolic extract	1000–5000 mg/kg	Albino rats with gentamicin-induced nephrotoxicity	Prevention in elevated serum creatinine and serum urea level and significant reduction in elevated level of urinary protein in albino rats.	[115]
27.	Muscle stimulant activity	Vasicine	1 &10 g/mL	Isolated uterus and mammary gland of rat/guinea pig.	Increase in amplitude of contractions in uterus, potentiated the action of oxytocin in mammary strip.	[116]
28.	Anticestodal activity	Whole plant: extract	800 mg/kg	Hymenolepis diminuta-rat experimental model	The reduction in eggs per gram count of 79.57 % and the percentage worm recovery rate of 16.60 % indicated that Adhatoda has anticestodal action.	[117]
29.	Anti-Alzheimer activity	Whole plant	294 μg/mL	in vitro: acetylcholinesterase (AChE) and cycloxygenase-1 (COX-1) enzymes	Adhatoda vasica showed inhibitory effect on AChE at IC50 294 μg/mL.	[118]
30.	Analgesic activity	Methanolic extract of leaves	200,400,600 mg/kg	Hot plate and tail immersion method in albino rats	Significantly (P < 0.05) inhibit the inhibition and pain in rats.	[91]
31.	Anthelmintic activity	Aqueous and ethanolic extracts of aerial parts	25–50 mg/mL	Gastrointestinal nematodes of sheep	The gastrointestinal nematode egg hatching and larval growth was inhibited more effectively by ethanolic extract at 50.0 mg/mL (P < 0.05).	[119]
32.	Antioxidant activity	Vasicine acetate	125–1000 μg/mL	1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay	Vasicine acetate had the highest radical-scavenging efficiency (66.15 %) at a concentration of 1000 μg/mL.	[120]
		Ethanolic extract of leaves	25–150 μg/mL	1,1-diphenyl-2-picrylhydrazyl (DPPH) Radical Scavenging Assay	69.23 % inhibition of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical was observed.	[121]

The details enumerated above in the table is indicative of the fact that the different plant parts demonstrate large number of pharmacological activities. As major number of activities have been conducted at the extract level, the possibilities and scope for further research is widened, viz through the identification of the active phytoconstituents responsible for the activities, conduction of clinical trials to validate the use of specific phytoconstituents like vasicine, vasicine acetate etc for their manifold therapeutic activities, comparison with prevailing drugs to assess the efficacy, and preparation of synthetic modification of compounds to enhance efficacy and reduce toxicity.

3.1. Bronchodilatory and antiasthmatic activities

Both in vivo and in vitro, vasicine and vasicinone exhibited bronchodilatory activity [97]. Bronchodilating effect of ethanolic extract of Adhatoda vasica was tested on histamine aerosol and acetylcholine induced broncho-constriction in guinea pigs. The broncho-dilating effect of A. vasica was found similar to ketotifen [79]. Hence, pyrrolo-quinazoline compounds like vasicine and vasicinone exerted potential antiasthamatic activity.

3.2. Wound-healing activity

Wound healing effect of methanolic, chloroform and diethyl ether extract ointment (10%w/w) of Adhatoda vasica was evaluated using excision wound model in albino rats. The methanolic extract ointment (10%w/w) showed significant effect as compared to the standard drug [99]. The chloroform and alcoholic extracts of Adhatoda vasica were also studied for wound healing potential on male buffalo calves. Increase in tensile strength, breaking strength, collagen, elastin and hydroxyproline etc. were observed [100]. Hence, Adhatoda vasica exerted potential wound healing activity.

3.3. Antiallergic activity

Some studies showed that alkaloids vasicinol and vasicine can inhibit significantly ovalbumin-induced allergic reactions [81]. Vasicinone has also proved to be efficient anti-allergen when studied on mice, guinea pigs and rats [82]. Compound 73/602 (AA), which is a structural analogue of vasicinone, possesses potent antiallergic activity in mice, rats and guinea pigs [122].

3.4. Anti-inflammatory activity

Anti-inflammatory potential of non-alkaloid fraction, methanol extract, alkaloids and saponins was established using modified hen's egg chorioallantoic membrane test. Alkaloid fraction displayed influential activity, whereas the methanolic extract alongwith the other fractions exhibited less activity [90]. The anti-inflammatory activity of vasicine, vasicinone, vasicine acetate, 2-acetyl benzyl amine, vasicinolone was conducted on carrageenan and CFA model induced paw oedema. Vasicinone at the dosage of 10.0 mg/kg in 4 days followed by CFA injection exhibited maximum inhibition rate (63.94 %) and vasicine at a dose of 20.0 mg/kg at 6 h after carrageenan injection, presented most effective anti-inflammatory properties (59.51 %) [73].

Vasicine is a pyrrolo-quinazoline alkaloid found as large as 12 % in the alkaloid fraction of Adhatoda vasica, thus proving it to be a potential therapeutic agent against different inflammation mediated diseases [123]. The alkaloid fraction exercises effective anti-inflammatory activity by deciphering the regulation of protein expression of some pro-inflammatory cytokines, mRNA down regulation and NO production inhibition. Further, clinical therapeutics in this direction will bring it as a potential anti-inflammatory agent.

3.5. Antimicrobial activity

The antimicrobial activity of vasicine, vasicinone, vasicine acetate, 2-acetyl benzyl amine, vasicinolone was assessed by using the microdilution method. Vasicine exhibited strong antibacterial activity at 20 g/mL dose against E. coli and also showed maximum antifungal activity against C. albicans at the dose of 55 g/mL [73].

Both 2-acetyl benzylamine and vasicine acetate were bioassayed against Mycobacterium tuberculosis exhibiting significant inhibition of the Mycobacterium species, one sensitive and one MDR (multi-drug-resistant) strain at 50 and 200 μg/mL, respectively [74]. Pyrrolo-quinazoline like vasicine and vasicine acetate have the potential to be developed as potent antimicrobial agents of future.

3.6. Abortifacient activity

Vasicine also displayed uterotonic activity. A study showed that vasicine started rhythmic contractions of human myometrial strips from both pregnant and non-pregnant uteri, similar to that of oxytocin and mathergin [3]. Another more study revealed that vasicine exhibited uterotonic and abortifacient effects on hamsters, rabbits, rats, and guinea pigs, basically due to increased synthesis and release of prostaglandins [93]. Hence, further study should concern about the utility of A. vasica as herbal drug.

3.7. Immunostimulant activity

Effect of alcoholic extract of leaves of Adhatoda vasica on splenic lymphocytes, peritoneal macrophages and haematological profile were examined in swiss albino mice by Thakur. Increase in splenic lymphocytes, blood lymphocytes, total WBC and peritoneal macrophages was observed [112]. Adhatoda displayed protective effect against cyclophosphamide induced myelosuppression and marginal increase in WBC count to a significant extent [113]. These studies suggested that Adhatoda vasica showed immunostimulant activity.

3.8. Hepatoprotective activity

Aqueous extract of A. vasica leaves at doses of 50–100 mg/kg displayed effective hepatoprotective activity on d-galactosamine induced damged liver in rats [103]. Recent study showed that hepatotoxicity due to anti-TB drugs can be ameliorated by ethanolic leaf extract of Adhatoda vasica Nees [124]. Hence, A. vasica can effectively abolish drug mediated hepatic impairments.

3.9. Antitussive activity

Muscle relaxing activity of essential oil of aerial parts of A. vasica on tracheal vascular smooth muscle of guinea pigs had been carried out by Cruz [125]. Further antitussive activity of A. vasica extract was studied on unanaesthetized and anaesthetized guinea pigs and rabbits. Action was found similar to codeine. It was suggested that it may be attributed to specific site of action of vasicinone and vasicine, which act on neuronal system and thus suppress coughing [102]. Therefore, mechanistic studies should be focused in this direction.

3.10. Prevention of aflatoxin-induced toxicity

Chemopreventive effect of leaf extract A. vasica was studied on aflatoxin B1 induced biochemical changes in the serum and liver of Wistar rats. Its potential to be used in the poultry industry to lower aflatoxicosis was demonstrated by the significant reduction in the activities of catalase and superoxide dismutase in liver tissues, the increase in the activities of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase, and the levels of cholesterol, VLDL, and LDL in blood serum [126].

3.11. Antibiotic property against fibroblasts

Vizic acid, psacbumin C, 8′z-enzyme conjuger, 5- (8′z, 11′z-heptodecadinyl) −1,3-benzinol, 9 '- (o-methyl) protocoteric acid and caliphenic acid isolated from Adathoda vasica were checked for their collagenase inhibition assay, elastase inhibition assay, hyaluronidase inhibition assay and tyrosinase inhibition assay by Ahmed et al. Their study revealed that the above isolated compounds can be used as novel antibiotics and can be further used in creams, lotions and tablets for future skin diseases control [127].

3.12. ACE inhibitory activity

Recently molecular docking studies of isolated pyrroquinazoline alkaloids viz. vasicinol, vasicine and vasicinone were carried out by Tehreem et al. Vasicinol showed binding as effectively as captopril, a standard drug of ACE inhibition. Vasicine displayed the highest ACE inhibitory activity and its IC₅₀ was 2.60 mM. The IC₅₀ values of vasicinol and vasicinone were found to be 6.45 and 13.49 mM, respectively [128].

3.13. Anti- Alzheimer activity

Anti-AChE activity was performed to elicit the possible role of the active compounds in the treatment of Alzheimer disease. Docking was carried out using a flexible ligand–rigid protein. Vasicine showed binding similar to tacrine and galantamine in the catalytic site and inhibited AChE reversibly and competitively with a Ki (inhibition constant) value of 11.24 μM, but vasicinone, vasicole, and anisotine shown weak or no binding. As a result, it can be utilized directly or indirectly to create effective anti-Alzheimer drugs [118].

3.14. Potential as repurposed drugs for COVID-19 like conditions

Recent studies by Gheware and coworkers [129] revealed that the aqueous extract of Adhatoda vasica (AV) can ameliorate the hyperinflammation and hypoxic features like thrombosis, lung injury and fibrosis, thus highlighting this herbal medicine as a potent repurposed drug for COVID-19 like conditions. The AV extract has beneficial effects on systemic inflammation and phenotypic features of the lungs, sounding the extracts to be useful for the COVID-19 pandemic situations. Anisotine and vasicoline of AV are found to be very good inhibitors when tested on protease inhibitor and replicase inhibitor of COVID-19 virus using COVID-19 Docking Server [130]. Six well-known alkaloids from AV were docked against SARS CoV-2 Mpro to study their binding properties. Only anisotine interacted with both the catalytic residues (His41 and Cys145) of Mpro and exhibited good binding affinity (−7.9 kcal/mol), thus revealing anisotine's potency to inhibit the proteolytic activity of SARS CoV-2 Mpro [131]. In another study, Adhatodine and vasnetine showed a binding affinity of −9.60 kJ/mol and −8.78 kJ/mol, respectively when docked with SARS-CoV-2 main protease (PDBID:6Y84), viral protein targets [132]. Recently the first clinical evidence of HIF-1 reduction in COVID-19 patients receiving AV herbal extract treatment established the potential of AV to be safe and efficacious interventions for COVID-19 [133]. The in-vitro and in-silico analysis strongly suggest that it may have the ability to inhibit the SARS-CoV2 infection and its progression sequelae, thus AV being relevant treatment to the global pandemic of the microscopic demon COVID-19.

4. Major milestone of Adosa chemistry

A number of pyrroloquinazoline alkaloids have been discovered from this plant. D. Hooper in 1888 first isolated the alkaloid vasicine. According to him the alkaloid occurs in the leaves as a salt with “adhatodic acid” [134]. Leaves of this plant has two major quinazoline alkaloid, vasicine and vasicinone [135]. Vasicine is one of the major bioactive alkaloid, present in the concentration of 1.3 %. Pharmacological investigations of vasicine showed bronchodilatory activity in vitro and in vivo both; while vasicinone showed only in vitro bronchodilatory activity [97]. Later in 1965, Inamdar et al. isolated a neutral, non-nitrogenous crystalline material viz. vasakin, which melts at 273–274֩ C with decomposition. Its pharmacological studies revealed that it obstructs the functioning of exogenous adrenaline, moreover it had local anesthetic activity, so it resembled atropine. But it varied from atropine as it depresses heart and was found to be nontoxic at higher doses [136]. In 1967, Huq et al. isolated β-sitosterol, tritricontane, adhatonine, anisotine, vasicinine, vasicine and vasicinone from the leaves of this plant. Other alkaloids such as vasicinone, vasicinol, adhatodinine, adhavasinone, vasicoline and vasicolinone [[137], [138], [139], [140], [141], [142]] have been isolated from its leaves and roots.

A new quinazoline alkaloid 1,2,3,9-tetrahydro-5-methoxypyrrolo [2,1-b]-quinazolin-3-ol was isolated from its leaves [141]. Flavonoids like isovitexin, astragaline, kaempferol, quercetin, as well as the triterpenoid α-amyrin have been detected from its flowers [137]. Dihydroxychalcone 4-glucoside was also isolated from the flowers of Adhatoda vasica in 1982 [142]. In addition to these, A. vasica also contains several other phytochemicals and miscellaneous compounds, as these are present in complex mixture. These discrepancies suggest that re-investigation of the chemical constituents of A. vasica will provide interesting information regarding the phytochemistry.

5. Compounds present in Adhatoda vasica

It is essential to identify which secondary metabolites are present in plant as it may provide a basis for its traditional uses. In more than 80 years of intensive research, a number of compounds have been isolated from different parts of the plant. Alkaloids are one of the major secondary metabolites, which are present in the form of pyrrolo-quinazoline derivatives (Fig. 3). In addition to these, Adosa also contains several other phytochemicals such as flavonoids (Fig. 4), terpenoids (Fig. 5), steroids (Fig. 6), chalcones (Fig. 7), lignins (Fig. 8), glucoside and galactoside, amino acids, phenolic acids, fatty acids, and other miscellaneous compounds. Here we have tabulated molecular formula and the part from which these compounds were isolated in Table 3.

Fig. 3.

Chemical structures of pyrroloquinazoline alkaloids.

Fig. 4.

Chemical structures of flavonoids.

Fig. 5.

Chemical structures of terpenoids.

Fig. 6.

Chemical structures of steroids.

Fig. 7.

Chemical structures of chalcones.

Fig. 8.

Chemical structures of lignins.

Table 3.

Compounds isolated from A. vasica.

S.No.	Compound name (Molecular formula)		Plant part & References
Pyrroloquinazoline alkaloids rowhead
1	Vasicine or Peganine (C11H12N2O)		Roots [143], Young plants [139], Leaves, Part not specified [144,145]
2	Vasicinone (C11H10N2O2)		Aerial parts [146], Leaves [ [135,[147], [148], [149]]], Part not specified, Roots [150]
3	1,2,3,9-tetrahydropyrrolo (2,1-b) quinazolin-9-one-3R hydroxy- 3 (2 dimethyl-amino) phenyl or Desmethoxyaniflorine (C19H19N3O2)		Leaves [151]
4	Adhatodine (C21H26N4O2)		Roots [143], Young plants [139], Leaves [ [152,153]]
5	Adhatonine (C20H21N3O2)		Leaves [147]
6	Adhavasinone (C12H12N2O3)		Leaves [141]
7	Anisotine (C20H20N4O3)		Roots [143], Young plants [139], Leaves [ [147,153]]
8	9-Acetamido-3,4-dihydropyrido-(3,4-b)-indole (C13H13N3O)		Roots [154]
9	Deoxyvasicine (C11H12N2)		Leaves [142]
10	Deoxyvasicinone (C11H10N2O)		Roots [154]
11	3-Hydroxyanisotine (C20H19N3O4)		Leaves [153]
12	5-Methoxy-vasicinone (C12H12N2O3)		Leaves [151]
13	7-Methoxy-3R-hydroxy-1,2,3,9-tetrahydropyrrolo-[2,1-b]-quinazolin-9-one (7-methoxy-vasicinone) (C12H12N2O3)		Leaves [151]
14	Peganidine (C14H16N2O2)		Aerial parts [151]
15	1,2,3,9-Tetrahydro-5-methoxy-pyrrolo [2,1-b] quinazoline-3-ol (C12H14N2O2)		Leaves [140]
16	Vasicoline (C19H21N3)		Leaves [152]; Young plants [139]
17	Vasicolinone (C19H19N3O)		Leaves [152]; Young plants [139]
18	Vasicol (1,2,3,4,9, 11-hexahydropyrrolo (2,1-b) quinazolin-3,11-diol, (C11H14N2O2)		Leaves [145]; Roots [150]; Leaves [153]
19	Vasicinolone (C11H10N2O3)		Roots [154]; Leaves [142]; Aerial parts [155]
20	Vasnetine (C19H17N3O3)		Leaves [153]
21	Vasicinol or 7-Hydroxypeganine (C11H12N2O2)		Roots [143]; Leaf [88]
22 23	Vasicine acetate (C13H14N2O2) Ethyl 4-quinazoline-2-carboxylate (C11H10N2O3)		Roots [75] Leaves [156]
Flavonoids rowhead
24		Apigenin (C15H10O5)	Aerial parts [157]
25		Astragalin or Kaempferol 3-β-d-glucopyranoside (C21H20O11)	Flowers [147]
26		Isovitexin (C21H20O10)	Leaves and Flowers [157]
27		Quercetin (C15H10O7)	Flowers [ [143,147,158]]
28		Kaempferol (C15H10O6)	Flowers [ [143,147,158]]
29		Rhamnosylvitexin (C27H30O14)	Flowers [143] Leaves and Flowers [157]
30		Vitexin (C21H20O10)	Leaves and Flowers [157]
31		Violanthin (C27H30O14)	Leaves and Flowers [157]
32 33 34		2″ O-Xylosylvitexin (C26H28O14) Kaempferol 3-O-sophoroside (C27H30O16) Luteolin (C15H10O6)	Leaves and Flowers [157] Flowers [159] Leaves and flowers [160]
Terpenoids rowhead
35		α-Amyrin (C30H50O)	Flowers [[143], [147], [158]]
36		β-Carotene (C40H56)	Part not specified [161]
37		3α-Hydroxy-Oleanane-5-ene (C30H50O)	Aerial parts [162]
38		3α -hydroxy-D-friedoolean-5-ene (C30H50O)	Aerial parts [146]
39		Epitaraxerol (C30H50O)	Leaves and Flowers [157], Aerial parts [146]
40 41 42 43 44		Taraxerone-14-ene (C30H48O) Neoandrographolide (C27H42O7) Caryophyllene (C15H24) Squalene (C30H50) Phytol (C20H40O)	Aerial parts [162] Leaves [163] Leaves [156] Leaves [156] Leaves [156]
Steroids rowhead
45		β-Sitosterol (C29H50O)	Roots, Aerial parts [162]
46 α-Sitosterol (C29H50O) Leaves [155] 47 Stigmasterol (C29H48O) Leaves [155] 48 Daucosterol (C35H60O6) Roots [143]
Chalcones rowhead
49		2′-Glucosyl-4-hydroxyl – oxychalcone (C21H22O8)	Roots [143]
50 51		2′,4-Dihydroxychalcone-4-O-β-d-glucopyranoside or 2′,4-Dihydroxychalcone 4-glucoside (C21H22O8) Hydroxyl oxychalcone (C15H10O3)	Flowers [142] Part not specified [164]
Lignins rowhead
52 53 54		Guaiacyl (polymer) Syringyl (polymer) p- Hydroxyl phenyl propane (polymer)	Wood [165] Wood [165] Wood [165]
Glucoside and Galactoside rowhead
55		Sitosterol-β-D-glucoside (C35H60O6)	Roots [154]
56		Ethyl-α-d-galactoside (C8H16O6)	Roots [154]
57		D-Glucoside (C6H12O6)	Roots [143]
58		d-Galactose (C6H12O6)	Roots [154]
59		β-glucoside-galactose (C12H22O11)	Roots [6]
60		β-Sitosterol-D-glucoside (C35H60O6)	Part not specified [6]
61		N oxide and glycoside of Vasicine (C11H12N2O2)	Aerial parts [166]
62		N oxide and glycoside of vasicinone (C11H10N2O3)	Aerial parts [166]
Amino acid rowhead
63		Betaine or vasicinine (C5H11NO2)	Flowers [147]
64		Amino-n-butyric acid (C4H9NO2)	Pollen [167]
65		Glycine (C2H5NO2)	Pollen [167]
66		Proline (C5H9NO2)	Pollen [167]
67		Serine (C3H7NO3)	Pollen [167]
68		Valine (C5H11NO2)	Pollen [167]
Phenolic acids rowhead
69		p-Hydroxybenzoic acid (C7H6O3)	Leaves [168]
70		Syringic acid (C9H10O5)	Leaves [168]
71		p-Coumaric acid (C9H8O3)	Leaves [168]
Fatty acids rowhead
72 73 74 75 76 77 78 79 80		Pentadecanoic acid (C15H30O2) Arachidic acid (C20H40O2) Behenic acid (C22H44O2) Lignoceric acid (C24H48O2) Cerotic acid (C26H52O2) Oleic acid (C18H34O2) Linoleic acid (C18H32O2) 9,12,15-Octadecatrienoic acid (C18H30O2) n- Hexadecanoic acid (C16H32O2)	Leaves [156] Seeds [169] Seeds [169] Seeds [169] Seeds [169] Seeds [169] Seeds [169] Leaves [156] Leaves [156]
Alkanones rowhead
81		3-Methylheptanone (C8H16O)	Flowers [164]
82		4-Heptanone (C7H14O)	Flowers [164]
Hydrocarbon rowhead
83 84		Tritriacontane (C33H68) 2-Cyclohexyl-eicosane (C26H52)	Roots [139] Leaves [156]
Alkyl Hydroxyketones rowhead
85		37-Hydroxy-hexatetracont-1-en-15-one (C46H90O2)	Aerial parts [155]
86		37-Hydroxy-hentetracontan-19-one (C41H82O2)	Aerial parts [155]
Vitamin rowhead
87		Vitamin C (C6H8O6)	Part not specified [161]
Alkanol rowhead
88 89		29-Methyl -triacontan-1-ol (C31H64O) 2,4- Dihydroxynonane (C9H20O2)	Aerial parts [162] Aerial parts [170]
Others rowhead
90		2-Acetyl benzyl amine (C9H11NO)	Roots [75]
91		1,3,5-Triazine-2,4,6-triamine (C3H6N6)	Leaves [171]
92		2,3-Dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (C6H8N4)	Leaves [171]
93		5-Hydroxymethylfurfural (C6H6O3)	Leaves [171]
94		2-Butylphenol (C10H14O)	Leaves [171]
95		3,4-Dihydroxy-5-methyl-dihydro-furan-2-one (C5H8O4)	Leaves [171]
96		2–(1,1-Dimethylethyl)-4-methoxyphenol (C11H16O2)	Leaves [171]
97		Megastigmatrienone (C13H18O)	Leaves [171]
98		Tetradecanoic acid (C14H28O2)	Leaves [171]
99		Vomifoliol (C13H20O3)	Leaves [171]
100		Oxalic acid, cyclobutylhexyl ester (C12H20O4)	Leaves [171]
101		Hexadecanoic acid (C16H32O2)	Leaves [171]
102		4-Ethyl-2-oxo-2,5,6,7-tetrahydro-1H-cyclopenta [B]pyridine-3-carbonitrile (C11H12N2O)	Leaves [171]
103		Vitamin E (C29H50O2)	Leaves [171]
104		1,2,3-Trimethyl benzene (C9H12)	Leaves [72]
105		Borneol (C10H18O)	Leaves [72]
106		Ethanonaphthalene (C12H10)	Leaves [72]
107		1,1,4a-Trimethyl-5,6-dimethylenedecahydronaphthalene (C15H24)	Leaves [72]
108		2-Tert-butyl-1,4-dimethoxybenzene (C12H18O2)	Leaves [72]
109		α-Caryophyllene (C15H24)	Leaves [72]
110		Caryophyllene oxide (C15H24O)	Leaves [72]
111		2-Naphthalenemethanol (C11H10O)	Leaves [72]
112		Stictic acid (C19H14O9)	Plant parts [172]
113		Usnic acid (C18H16O7)	Plant parts [172]
114		Epigallocatechin gallate (C22H18O11)	Plant parts [172]
115		Epigallocatechin (C15H14O7)	Plant parts [172]
116		Catechin (C15H14O6)	Plant parts [172]
117		Epicatechin (C15H14O6)	Plant parts [172]
118		Morin (C15H10O7)	Plant parts [172]
119		Naringenin (C15H12O5)	Plant parts [172]
120		Viscic acid (C5H10O2)	Leaves and seeds [172]
121		Pasakbumin (C20H24O9)	Leaves and seeds [172]
122		8′Z-Enyl congener (C18H16O7)	Leaves and seeds [172]
123		5-(8′Z,11′Z-heptadecadienyl)-1,3- benzene diol (C23H34O2)	Leaves and seeds [172]
124		9'-(O-Methyl) protocetraric acid	Leaves and seeds [172]
125		Calophynic acid (C15H10O7)	Leaves and seeds [172]

Some recent studies also showed that ethyl acetate extract of Adhatoda vasica helps to maintain the redox homeostasis of hepatic cells hence it can be well-thought-out as an effective candidate against liver disorders due to oxidative stress [173]. Another study showed that pyrroquinazoline alkaloids like vasicine, vasicinone and deoxyvasicine have 5-LOX inhibitory potential [174]. All studies suggested that this plant is rich source of pyrroloquinazoline derivatives and their pharmaceutical applications prove that these candidates have the potential to develop as drugs. It is necessary to study the structure activity relation of the active chemical constituents for discovery and design of novel drugs with improved efficacy from traditionally vital natural products/plant Adhatoda vasica.

6. Conclusion and future directions

The present review summarizes the traditional importance, folklore uses, research progress in pharmacology and phytochemistry, importance in Ayurvedic and Unani medicinal systems, and scope for future research related to Adhatoda vasica. This plant has been used for a variety of disorders including; cold, cough, asthma, whooping cough, chronic bronchitis, heart troubles etc. Merit of many of therapeutic applications relates to important alkaloids of AV viz. vasicine, vasicinol, anisotine etc. After reviewing we came across the following areas where further research can be supervised. (1) Investigation regarding inception time of traditional uses. (2) Further in-depth clinical trials of important pharmacological activities viz anti-asthamatic and bronchodilatory. (3) Analysis of the structure activity relationships of pyrrolo-quinazoline alkaloids. In view of its multiple uses, more activity screening and structure-activity relationship studies are to be explored. (4) Many scientific reports suggested that vasicine has abortifacient and oxytocic effects. Therefore, further research may be focused on toxicity and safety of A. vasica as an herbal medicine. (5) Recent studies reveal that AV has potential to be developed as repurposed drugs for COVID-19 like conditions, further clinical trials can be carried out in this direction as WHO has declared JN.1 covid variant as variant of interest. (6) Synthetic modification of the compounds having important therapeutic activities like vasicine, vasicinol and anisotine can be conducted to increase their efficacy. (7) As this plant represents a class of herbal drugs with very strong conceptual or traditional as well as a strong experimental base for its use without any harm in human beings, hence it would be a matter of interest for chemists to isolate potent bioactive compounds from Adosa as a potential phyto-pharmaceutical agent for preventing ailments. Adhatoda vasica being biologically rich in pyrroloquinazoline alkaloids develops possibilities for further research through in vivo and in silico studies to confirm the therapeutic usefulness or medication potency of these bioactive compounds. The review validates the ethnomedicinal, phytochemical and pharmacological significance of Adhatoda vasica in management of different ailments in humans.

Consent for publication

Not applicable.

CRediT authorship contribution statement

Poonam Khandelwal: Writing – review & editing, Writing – original draft, Supervision, Conceptualization. Barkha Darra Wadhwani: Writing – review & editing. Ravindra Singh Rao: Writing – review & editing. Deepak Mali: Writing – review & editing, Investigation. Pooja Vyas: Writing – review & editing, Writing – original draft. Tarun Kumar: Writing – review & editing. Rashmy Nair: Writing – review & editing, Supervision.

Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Barkha Darra Wadhwani reports financial support was provided by India Ministry of Science & Technology Department of Science and Technology. Poonam Khandelwal reports administrative support was provided by Ministry of Education and SPD-RUSA Rajasthan. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.