Bioactivities from Marine Algae of the Genus Gracilaria

Abstract

Seaweeds are an important source of bioactive metabolites for the pharmaceutical industry in drug development. Many of these compounds are used to treat diseases like cancer, acquired immune-deficiency syndrome (AIDS), inflammation, pain, arthritis, as well as viral, bacterial, and fungal infections. This paper offers a survey of the literature for Gracilaria algae extracts with biological activity, and identifies avenues for future research. Nineteen species of this genus that were tested for antibacterial, antiviral, antifungal, antihypertensive, cytotoxic, spermicidal, embriotoxic, and anti-inflammatory activities are cited from the 121 references consulted.

1. Introduction

The ocean environment contains over 80% of world’s plant and animal species [1] and with more than 150,000 seaweeds found in the intertidal zones and tropical waters of the oceans, it is a primary source of natural products [2].

Seaweeds are floating and submerged plants of shallow marine meadows. They have salt tolerance because the osmolarity of cytoplasm is adjusted to match the osmolarity of the seawater so that desiccation does not occur. They lack true stems, roots and leaves; however, they possess a blade that is leaf like, a stipe that is stem like, and a holdfast that resembles roots like terrestrial plants. Seaweeds contain photosynthetic pigments and use sunlight to produce food and oxygen from carbon dioxide, and the water [3].

Marine macroalgae are important ecologically and commercially to many regions of the world, especially in Asian countries such as China, Japan and Korea [4]. They are a valuable food resource which contains low calories, and they are rich in vitamins, minerals, proteins, polysaccharides, steroids and dietary fibers [5–7]. Since as early as 3000 BC, they were also considered important as traditional remedies [4]. The Japanese and Chinese use brown algae in the treatment of hyperthyroidism and other glandular disorders [8–11]. The unsaturated lipids afford protection against cardiovascular pathogens [12].

Seaweeds have been one of the richest and most promising sources of bioactive primary and secondary metabolites [13] and their discovery has significantly expanded in the past three decades [4,14,15]. The algae synthetize a variety of compounds such as carotenoids, terpenoids, xanthophylls, chlorophyll, vitamins, saturated and polyunsaturated fatty acids, amino acids, acetogenins, antioxidants such as polyphenols, alkaloids, halogenated compounds and polysaccharides such as agar, carrageenan, proteoglycans, alginate, laminaran, rhamnan sulfate, galactosyl glycerol and fucoidan [16–25].

These compounds probably have diverse simultaneous functions for the seaweeds and can act as allelopathic, antimicrobial, antifouling, and herbivore deterrents, or as ultraviolet-screening agents [26]. They are also used by the pharmaceutical industry in drug development to treat diseases like cancer, acquired immune-deficiency syndrome (AIDS), inflammation, pain, arthritis, infection for virus, bacteria and fungus [27]. Currently, algae represent about 9% of biomedical compounds obtained from the sea [28].

Compounds with cytostatic, antiviral, antihelmintic, antifungal and antibacterial activities have been detected in green, brown and red algae [29,30]. The algae produce pure forms of the fatty acids found in human milk that appear to be building blocks for mental and visual development [31] and have been extensively screened for syntheses of new drugs [32,33].

During the 1970s, Ryther and collaborators evaluated numerous species of red, green and brown macroalgae for their potential growth rates and dry weight yields [34]. They demonstrated that the genus Gracilaria was the most attractive candidate because of its ability to achieve high yields and while producing commercially valuable extracts [35].

Gracilaria Greville genus (Gracilariales, Rhodophyta) is a macroalgae group with more than 300 species of which 160 have been accepted taxonomically. These are usually red, green or greenish brown with a three-phase cycle and can be found in tropical and subtropical seas [36,37].

The Gracilaria species are important for the industrial and biotechnological uses because they have phycocolloids, the main source of agar α-(1,4)-3,6-anhydro-l-galactose and β-(1,3)-d-galactose with little esterification in cell wall [2,38]. Among the carbohydrates, agar and other polysaccharides are present in G. confervoides [39], G. dura [40], G. chilensi and G. secundata [41,42].

These algae also produce important bioactive metabolites like the primary compound with antibiotic activity acrylic acid [43], and the eicosanoids which are derivatives C₂₀ polyunsaturated fatty acid (PUFA) metabolism through oxidative pathways that originate mainly from arachidonic acid and eicosapentaenoic acids, the precursors of prostaglandins (PGs) [44,45]. Species such as G. asiatica and G. lichenoids contain PGE₂ [46,47]. PGF₂ and 15-keto-PGE₂ were respectively isolated from G. lichenoids and G. asiatica [45]; G. verrucosa contains PGA₂ that appears to be responsible for a gastrointestinal disorder, known as “ogonori” poisoning in Japan [48].

Lipids are abundant in this genus being mainly prostaglandins [49], steroids, such as cholesterol and clinoasterol are present in G. crassa and G. coronopifolia respectively [50–52], as well as G. longa [48,53–57] and G. dura. Other steroids such as 3-beta-hydroxy-poriferast-5-en-7-one, 3-beta-7-alpha-diol-poriferast-5-ene and 5-alpha-poriferast-9(11)-en-3-beta-ol are isolated from G. dura [50]; cholestane-3-β-5-diol,5-α:24(S)-ethyl [52], poriferastene 8 [50], poriferast-5-ene-3-β-7-β-diol [51] and poriferast-5-ene-3-β-7-α-diol [51] were identified in G. coronopifolia; G. longa also has a variety of compounds like alpha linolenic acid, gamma linolenic acid [58], glycolipids [59], 5-dehydro avenasterol, fucosterol, myristic acid, desmosterol and 5-alpha-24(S)-ethyl-cholestane-3-beta-6-beta-diol [60]. Phytochemical studies with extracts from fresh thallus of G. andersoniana showed the following isolates: oleic acid, linoleic acid, cholesterol, prostaglandin A₂, prostaglandin E₂, leukotriene B₄ and phytol [61–63].

Studies with G. asiatica reported the diterpenes cis and trans-phytol [63]. A variety of lactones are present in Gracilaria from the Pacific Ocean, such as aplysiatoxin isolated from G. confervoides [64,65], polycavernoside B, polycavernoside B₂, and polycavernoside A₂ and A₃ isolated from G. crassa [49,66]. Other constituents are also containedin this genus such as proteins r-phycoerythrin from G. salicornia [67] and G. longa [68], gigartinine from G. chilensis [69] and proteoglycan from G. longa [70].

The possibility of finding new molecules from natural products is immeasurable. For this reason the plants and their derivatives are major sources of all drugs, affecting about 30% of pharmaceutical market [71]. According to Newman et al. (2003), between the years 1981 and 2002, 877 new molecules were introduced into the market, with 49% of substances isolated from natural sources followed by semi-synthetic derivatives or synthesized molecules taking the structures of natural origin as models [29].

The search for new effective medicines remains a challenge for scientists. Therefore around the world, many researchers have focused on natural sources for new molecules with algae among the targets of these studies. So in this study we reviewed the literature related to bioactivities for Gracilaria algae.

2. Results and Discussion

In this review, among the 160 species of Gracilaria already identified taxonomically, only 19 of them had their extracts and fractions chemically tested for toxicity, cytotoxic, spermicidal, antiimplantation, antibacterial, antiviral, antifungal, antiprotozoa, antihypertensive, antioxidant, anti-inflammatory, analgesic, and spasmolytic effects in gastrointestinal tract (Table 1).

Table 1.

Bioactivities of marine algae of the Gracilaria genus.

Botanical Name	Part used	Type of extract	Bioassays models, organism, dose or route of administration	Result
Studies of toxicity
Gracilaria bursa-pastoris (S.G.Gmelin) P.C.Silva	FzDTh	H2O Ext.	Cytotoxic activity-cell culture-10.0 μg/mL	Inactive [72]
	FTh	95% EtOH Ext. or CHCl3 Ext.	Cytotoxic activity-cell culture-10.0 μg/mL	Inactive [72]
Gracilaria chorda (Holmes)	FsO	H2O Ext.	Toxicity assessment-mouse-1.2 mg/animal-i.p.	Active [48]
Gracilaria coronopifolia (J. Agardh)	FTh	Plant	Toxic effect-human adult-oral	Active [65]
Gracilaria corticata (J.Agardh) J.Agardh	Th	50% EtOH-H2O Ext.	Toxicity assessment-mouse-DL50 1000 mg/kg-ip	Active [73]
Gracilaria domingensis (Kützing) Sonder ex Dickie	DO	90% EtOH Ext.	Cytotoxity-Artemia salina L.-200 μg/mL	Active [74]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	DTh	Plant	Toxicity effect (death)-human adult-oral	Active [49]
	SDTh	90% EtOH Ext.	Toxicity assessment-mouse-DL50 0.825 mg/kg-i.p.	Active [75]
Gracilaria foliifera (Forsskål) Borgesen	DEP	(1:1) EtOH-H2O Ext.	Cytotoxic activity-cell culture-dose: dry weight of plant	Active [76]
Gracilaria textorii (Suringar) De Toni	FzDO	MeOH Ext.	Cytotoxic activity-cell culture (CA 9 KB)	Inactive [77]
	FsTh	Hexane Ext.	Cytotoxic activity-culture cell (LEUK P 388)-ED 50 > 100 μg/mL	Equivocal [78]
		CCl4 Ext.	Cytotoxic activity-culture cell (LEUK P 388)-ED 50 22.2 μg/mL	Equivocal [78]
		CHCl3 Ext.	Cytotoxic activity-culture cell (LEUK P 388)-ED 50 32.2 μg/mL	Inactive [78]
Gracilaria verrucosa (Hudson) Papenfuss	DO	H2O Ext.	Toxicity assessment-mouse-1.2 mg/animal-i.p.	Active [48]
	FzDO	MeOH Ext.	Cytotoxic activity-cell culture (CA 9 KB)	Inactive [77]
	FO	30% EtOH Ext.	Cytotoxic activity-cell culture (CA 9 KB)-10.0 μg/mL	Inactive [79]
		(1:1) CHCl3-MeOH Ext.	Cytotoxic activity-cell culture (CA 9 KB)-1.0 μg/mL	Equivocal [79]
	FTh	H2O Ext. and 95% EtOH Ext.	Cytotoxic activity-cell culture (LEUK P 388-P 3)-10.0 μg/μL	Inactive [72]
Effects on the nervous system
Gracilaria corticata J.Agardh	SDTh	90% EtOH Ext.	Autonomic effects-dog-50 mg/kg-iv	Inactive [75]
			CNS effects-mouse	Inactive [75]
			Analgesic activity-mouse	Inactive [75]
			Anticonvulsant activity-mouse	Inactive [75]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Autonomic effects-dog-50 mg/kg-iv	Inactive [75]
			CNS effects-mouse	Inactive [75]
			Analgesic activity-mouse	Inactive [75]
			Anticonvulsant activity-mouse	Inactive [75]
Gracilaria verrucosa (Hudson) Papenfuss	SDTh	90% EtOH Ext.	CNS effects-mouse	Inactive [75]
Contraception activity
Gracilaria corticata J.Agardh	DTh	(1:1) MeOH-CH2Cl2 Ext.	Embryotoxic effect-pregnant rat-1.0 mg/kg-intragastric	Inactive [80]
	SDTh	90% EtOH Ext.	Antiimplantation effect-pregnant rat-100.0 mg/kg	Inactive [75]
			Spermicidal effect-rat-2.0 %	Inactive [75]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Antiimplantation effect-pregnant rat-100.0 mg/kg	Inactive [75]
			Spermicidal effect-rat-2.0%	Inactive [75]
Gracilaria verrucosa (Hudson) Papenfuss	SDTh	90% EtOH Ext.	Spermicidal effect-rat-2.0%	Inactive [75]
Anti-inflammatory activity
Gracilaria textorii (Suringar) De Toni	EP	H2O Ext.	Platelet aggregation inhibition (adenosine diphosphate; arachidonic acid or collagen stimulation)-100.0 μg/mL	Inactive [81]
			Venotonic activity (platelet aggregating factor stimulation)-100.0 μg/mL	Inactive [81]
Gracilaria verrucosa (Hudson) Papenfuss	DTh	Polysaccharide fraction	Immunostimulant activity-mouse-4.0 mg/animal-i.p.	Active [82]
			Phagocytosis stimulation-mouse-4.0 mg/animal-i.p.	Active [82]
	SDTh	90% EtOH Ext.	Antiinflammatory activity-rat-intragastric	Inactive [75]
Antioxidant activity
Gracilaria verrucosa (Hudson) Papenfuss	Plant	MeOH Ext.	Radical scavenging effect (DPPH radicals)-IC50 480.0 μg	Active [83]
	DTh	Polysaccharide fraction	Oxygen radical formation induction-mouse-4.0 mg/animal-i.p.	Active [82]
Gastrointestinal effects
Gracilaria chorda (Holmes)	FsO	H2O Ext.	Mouse-0.5 mg/animal-gastric intubation and dose 0.5 mg/loop-i.p.	Active [48]
Gracilaria verrucosa (Hudson) Papenfuss	DO	H2O Ext.	Mouse-0.5 mg/animal-gastric intubation	Active [48]
Cardiovascular effects
Gracilaria corticata (J.Agardh) J.Agardh	SDTh	90% EtOH Ext.	Cardiovascular effects-dog-50 mg/kg-iv	Inactive [75]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Cardiovascular effects-dog-50 mg/kg-iv	Inactive [75]
			Diuretic activity-rat-intragastric	Active [75]
Gracilaria lichenoides (Greville)	EP	H2O Ext.	Antihypertensive activity-rat-iv	Active [84]
	FsTh	H2O Ext.	Antihypertensive activity-rat-iv	Active [85]
Gracilaria verrucosa (Hudson) Papenfuss	SDTh	90%EtOH Ext.	Cardiovascular effects-dog-50 mg/kg-iv	Inactive [75]
Hypoglycemic activity
Gracilaria corticata J.Agardh	SDTh	90% EtOH Ext.	Rat-250 mg/kg – intragastric	Inactive [75]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Rat-250.0 mg/kg – intragastric	Inactive [75]
Anti-enzymes activity
Gracilaria arcuata (Zanardini)	DTh	MeOH Ext.	Tyrosinase inhibition-0.33 mg/mL	Inactive [86]
Gracilaria corticata (J.Agardh) J.Agardh	DO	PET Ether Ext.; CHCl3 Ext. or MeOH Ext.	Penicillinase inhibition-1.0 μg/units	Inactive [87]
Gracilaria textorii (Suringar) De Toni	EP	H2O Ext.	Aldose reductase inhibition-10.0 μg/mL	Inactive [81]
	FzDO	MeOH Ext.	Cyclic AMP phosphodiesterase inhibition	Inactive [77]
Gracilaria verrucosa (Hudson) Papenfuss	FzDO	EtOAc Ext.	Lipase inhibition	Equivocal [88]
		MeOH Ext.	Cyclic AMP phosphodiesterase inhibition	Inactive [77]
Respiratory effects
Gracilaria corticata (J.Agardh) J.Agardh	SDTh	90% EtOH Ext.	Respiratory depressant-dog-50 mg/kg-iv	Inactive [75]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Respiratory depressant-dog-50 mg/kg-iv	Inactive [75]
Gracilaria verrucosa (Hudson) Papenfuss	SDTh	90% EtOH Ext.	Respiratory depressant-dog-50.0 mg/kg-iv	Inactive [75]
Spasmolytic activity
Gracilaria corticata (J.Agardh) J.Agardh	SDTh	90% EtOH Ext.	Spasmolytic activity-guinea pig	Inactive [75]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Negative chronotropic effect-dog-50.0 mg/kg-iv	Inactive [75]
Antibacterial activity
Gracilaria cervicornis (Turner) J.Agardh	DEP	95% EtOH Ext.	Agar plate-Staphylococcus aureus-5.0 mg/mL	Active [89]
			Agar plate-Proteus vulgaris; Escherichia coli; Aspergillus fumigates; Candida albicans; Pseudomonas aeruginosa; Streptococcus pyogenes- 50.0 mg/mL	Inactive [89]
Gracilaria corticata (J.Agardh) J.Agardh	DO	PET Ether Ext.; CHCl3 Ext. or MeOH Ext.	Agar plate-Staphylococcus aureus; Escherichia coli-MIC >200 μg/mL	Inactive [90]
	FsO	MeOH Ext.	Agar plate-Escherichia coli; Salmonella paratyphi A; Salmonella paratyphi B; Shigella sonnei	Inactive [91]
			Agar plate-Bacillus subtilis; Staphylococcus aureus; Bacillus megaterium; Streptococcus viridans	Active [91]
	SDTh	90% EtOH Ext.	Agar plate-Klebsiella pneumonia; Pseudomonas aeruginosa; Staphylococcus aureus; Escherichia coli; Streptococcus faecalis	Inactive [75]
Gracilaria debilis (Forsskål) Borgesen	DO	95% EtOH Ext.	Agar plate-Escherichia coli; Staphylococcus aureus	Active [92]
			Agar plate-Mycobacterium smegmatis Inactive	[92]
Gracilaria domingensis (Kützing) Sonder ex Dickie	DO	95% EtOH Ext.	Agar plate-Escherichia coli; Staphylococcus aureus	Active [92]
		Acetone Ext. or Ether Ext.	Agar plate-Escherichia coli; Staphylococcus aureus	Inactive [92]
		95% EtOH Ext. or Acetone Ext.	Agar plate-Mycobacterium smegmatis	Active [92]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Agar plate-Escherichia coli; Streptococcus faecalis; Staphylococcus aureus; Pseudomonas aeruginosa; Klebsiella pneumoniae	Inactive [75]
Gracilaria pygmea (Borgesen)	FsO	MeOH Ext.	Agar plate-Bacillus subtilis; Staphylococcus aureus; Escherichia coli; Salmonella paratyphi A; Streptococcus viridans; Shigella sonnei; Salmonella paratyphi B	Inactive [91]
			Agar plate-Bacillus megaterium	Active [91]
Gracilaria sjoestedii (Kylin)	DO	95% EtOH Ext.	Agar plate-Escherichia coli; Staphylococcus aureus	Active [92]
			Agar plate-Mycobacterium smegmatis	Inactive [92]
Gracilaria tikvahiae McLachlan	DEP	CHCl3 Ext. or EtOH Ext.	Agar plate -Staphylococcus aureus	Active [93]
			Agar plate-Streptococcus faecalis; Pseudomonas aeruginosa	Inactive [93]
Gracilaria verrucosa (Hudson) Papenfuss	FTh	**	Agar plate-Vibrio marinofulvis; Micrococcus imfimus; Pseudomonas atlantica-40.0 μg/μL	Inactive [94]
	Th	70% EtOH Ext.	Antiphage activity-agar plate-Bacteriophage T 1; Bacteriophage T 2; Bacteriophage T 4; Bacteriophage T 7; Bacteriophage MS 2; Bacteriophage PHI-CHI 174-0.50 μg/mL	Inactive [95]
Antifungal activity
Gracilaria corticata (J.Agardh) J.Agardh	FsO	MeOH Ext.	Agar plate-Aspergillus niger; Fusarium solani; Alternaria solani; Penicillium funiculosum	Inactive [91]
	SDTh	90% EtOH Ext.	Agar plate-Sporotrichum schenckii; Cryptococcun neoformans; Candida albicans; Trichophyton mentagrophytes; Aspergillus fumigates	Inactive [75]
Gracilaria debilis (Forsskål) Borgesen	DO	95% EtOH Ext.	Agar plate-Candida albicans	Active [92]
			Agar plate-Neurospora crassa	Inactive [92]
Gracilaria domingensis (Kützing) Sonder ex Dickie	DO	95% EtOH Ext. and Acetone Ext.	Agar plate-Candida albicans; Neurospora crassa	Active [92]
		Ether Ext.	Agar plate-Candida albicans	Inactive [92]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Agar plate-Sporotrichum schenckii; Candida albicans; Cryptococcus neoformans; Trichophyton mentagrophytes; Aspergillus fumigates	Inactive [75]
Gracilaria pygmea (Borgesen)	FsO	MeOH Ext.	Agar plate-Aspergillus niger; Fusarium solani; Alternaria solani; Penicillium funiculosum	Inactive [91]
Gracilaria sjoestedii (Kylin)	DO	95% EtOH Ext.	Agar plate-Candida albicans	Active [92]
			Agar plate-Neurospora crassa	Inactive [92]
Gracilaria tikvahiae McLachlan	DEP	CHCl3 Ext. and EtOH Ext.	Agar plate-Candida albicans	Active [93]
Antiviral activity
Gracilaria bursa-pastoris (S.G.Gmelin) P.C.Silva	FzDTh	**	Cell culture-Herpes simplex 1 and HIV Virus	Inactive [96]
Gracilaria corticata (J.Agardh) J.Agardh	Th	50% EtOH-H2O Ext.	Cell culture-Semlicki-forest Virus-0.05 mg/mL	Equivocal [73]
			Cell culture-Ranikhet and Vaccinia Virus-0.05 mg/mL	Inactive [73]
	SDTh	90% EtOH Ext.	Cell culture-Ranikhet Virus	Inactive [75]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Cell culture-Semlicki-forest and Ranikhet Virus	Inactive [75]
Gracilaria pacifica (I. A. Abbott)	DO	MeOH Ext.	Cell culture-Herpes simplex 1 Virus-400.0 μg/mL	Inactive [97]
			Cell culture-Virus sindbis-200.0 μg/mL	Active [97]
Gracilaria species	FzDTh	**	Cell culture-Herpes simplex 1 and HIV Virus	Inactive [96]
Gracilaria textorii (Suringar) De Toni	FzDO	MeOH Ext.	Cell culture-Herpes simplex 1 Virus	Inactive [77]
	Th	H2O Ext.	Cell culture-HIV Virus-MIC > 1000 μg/mL	Inactive [98]
	Fresh	MeOH Ext.	Epstein-Barr virus early antigen activation inhibition (telocidin b-4 induced	** [99]
	Th		Epstein-Barr virus induced activation)-4.0 μg/mL
Gracilaria verrucosa (Hudson) Papenfuss	FzDO	MeOH Ext.	Cell culture-Herpes simplex 1 Virus	Inactive [77]
Antiprotozoal activity
Gracilaria corticata (J.Agardh) J.Agardh	SDTh	90% EtOH Ext.	Agar plate-Entamoeba histolytica; Plasmodium berghei	Inactive [75]
Gracilaria edulis (S.G.Gmelin) P.C.Silva	SDTh	90% EtOH Ext.	Agar plate-Entamoeba histolytica; Plasmodium berghei	Inactive [75]
Allelophatic activity
Gracilaria compressa (C.Agardh) Greville	DEP	95% EtOH Ext.	Agar plate-Helianthus tuberosus-dose: dry weight of plant	Active [76]
Gracilaria foliifera (Forsskål) Borgesen	DEP	H2O Ext.	Agar plate-Helianthus tuberosus-dose: dry weight of plant	Active [76]
Gracilaria verrucosa (Hudson) Papenfuss	DEP	95% EtOH Ext.	Agar plate-Helianthus tuberosus-dose: dry weight of plant	Active [76]

Legend: DEP = Dried entire plant; DO = Dried organism; DTh = Dried thallus; EP = Entire plant; FO = Frozen organism; FsO = Fresh organism; FsTh = Fresh thallus; FTh = Frozen thallus; FzDO = Freeze dried organism; FzDTh = Freeze Dried thallus; SDTh = Shade dried thallus; Th = Thallus; PET Ether);

^**= Not stated.

These biological studies were mainly developed in Japan and Brazil. This fact is justified by the extensive coastlines and marine biodiversity and is influenced by several factors for the development of these species, such as temperature, radiation, salinity, metal ions and other chemically fundamental components. Australia and Guam have recently become interested in the study of algae and diverse marine species. The consumption of algae has increased in European countries in recent decades with 15 to 20 species of algae being marketed in Italy, France and Greece. In western countries like Venezuela, USA and Canada, the macroalgae are industrially used as a source of hydrocolloids agar, carrageenan and alginate [100]. Carrageenan has been found to be useful in ulcer therapy and alginates are known to prolong the period of activity of certain drugs [8–11].

2.1. Studies of Toxicity

In France, extract studies with ethanol/water draw up from dried entire plant of G. foliifera showed toxicity in humans when treated with oral dose and cytotoxicity studies [75,76]. G. coronopifolia and G. edulis were also toxic to humans [65,49] (See Table 1). Carbohydrate, heparin [97], agar [101], manauealide A, manauealide B [64], manauealide C [102], palmitic, palmitoleic, oleic, lauric and myristic acids [103], steroids and alkaloids malyngamide [104] were found in these species (Figure 1).

Figure 1.

Structure of the compounds found in G. foliifera, G. coronopifolia and G. edulis.

There is currently a tendency to substitute the use of laboratory animals in toxicological tests with alternative methods to reduce their numbers in experiments, or refine the existing methodology in order to minimize pain and stress [105]. A rapid and effective alternative to realize primary toxicity and biological action screening of compounds is the estimation of the 50% lethal concentration (LC₅₀) through brine shrimp assay using Artemia salina L. [106]. A 90% ethanol extract of G. domingensis had LC₅₀ of 200 μg/mL against A. salina [74].

Another method to evaluate toxicity is determining cytotoxic activity. In this context aqueous extract from dried thallus of G. bursa-pastoris (10.0 μg/mL), chloroform and methanol extracts from G. textorii, which was isolated steroid cholest-4-en-3-one [107], and ethanol extract from G. verrucosa were not toxic in cell culture. However, aqueous extract from G. verrucosa at a dose of 1.2 mg/animal showed toxicity to mice [48], according to Table 1. In this seaweed, lipids were indentified, such as PGF_α [84,85], glycerol, ethanolamine-phosphatidyl [58], choline-phosphatidyl [58,108], ethanol-phosphatidyl [58], floridoside [109], and carbohydrates, such as agar [110–113] (Figure 2).

Figure 2.

Structure composed of species of Gracilaria tested in cytotoxicity.

2.2. Effects on the Nervous System

Studies related to nervous system are important to understanding and treat complex degenerative and behavioral diseases. 90% ethanol extracts from G. corticata, G. edulis and G. verrucosa did not cause central or periphery effects for mice or dogs (50 mg/kg), and did not show analgesic or anticonvulsant activities for mice [75] (Table 1).

2.3. Contraception Activity

The researchers have also investigated new molecules with anticonceptive action; the post-coital contraceptive action of marine seaweeds was also evaluated in animals. Methanol: methylene chloride (1:1) extract from G. corticata was orally administered at 500 or 1000 mg/kg/day to female rats from day 1 to day 7 of their pregnancies. Higher doses produced significant post-coital contraceptive activity due to enhanced pre-implantation without any marked side effects. These findings indicate that red marine algae are a potential source for post-coital contraceptive drugs [80].

90% Ethanol extracts from G. edulis (100 mg/kg) and G. corticata were inactivated before the antiimplantation effect when they tested in pregnant rats [75,80]. Ethanol extracts from shade dried thallus of G. edulis and G. verrucosa were inactive in spermicidal bioassays [75]. Extracts from G. edulis showed 100% inhibition of sperm motility and this effect was related to disruption of the plasma membrane by spermicidal compounds [3] (Table 1).

2.4. Anti-Inflammatory and Antioxidant Activities

The anti-inflammatory activity of seaweeds has been studied. Polysaccharide fractions from G. verrucosa at a dose of 4.0 mg/animal were orally and intraperitoneally administered to mice and showed immunopotentiating activity stimulating phagocytosis [82]. Methanol extract and polysaccharide fractions from G. verrucosa were also antioxidant [82,83]. Aqueous extract from G. textorii at a dose of 100 μg/mL did not inhibit platelet aggregation induced by adenosine diphosphate, arachidonic acid or collagen [81]. G. verrucosa, G. asiatica, G. lichenoides and others species contain PGE₂ [47,85], that have physiological effects including hyperthermia, hypotension, smooth muscle dilatation, hyperalgesia and gastric secretion inhibition [114,115] (Table 1).

2.5. Gastrointestinal Effects

Aqueous extract from dried G. verrucosa algae or fresh G. chorda algae at a dose of 0.5 mg/animal controlled gastrointestinal disorders in mice [48] (Table 1), resulting from zeaxanthin and antheraxanthin [116], carotenoids, pyrimidine 2-amino-4-carboxy, non-alkaloid nitrogen heterocycle [90], steroids, 5-alpha-poriferastane, 3-beta-6-alpha-diol poriferastane, 5-alpha-3-beta-6-beta-diol [51] and gigatinine [85] (Figure 3).

Figure 3.

Structure of the compounds found in G. verrucosa and G. chorda.

2.6. Cardiovascular Effects

90% Ethanol extracts from G. corticata, G. edulis and G. verrucosa showed no cardiovascular effects in dogs (50 mg/kg) [75]. 90 % ethanol extract from G. edulis showed diuretic activity [75]. Aqueous extract from G. lichenoides was administered intravenously in rats and it was antihypertensive [84]. Tyrosinase inhibition was not induced by methanol extract from G. arcuata [86] and aqueous extract from G. textorii, 10 μg/mL, was negligable on aldose reductase [83] (Table 1).

2.7. Antibiotic Activity

Extracts or ingredients from various algae have shown antibacterial activity in vitro against gram-positive and gram-negative bacteria [117]. The agar disc diffusion method for antibacterial susceptibility was used for evaluation and 6 mm discs were impregnated with 20 μL of the extracts and placed in inoculated Muller Hinton agar. Antibacterial activity from chloroform extract of G. edulis (Gmelin) Silva was tested against bacterial strains of Vibrio cholera, Staphylococcus aureus, Shigella dysenteriae, Shigella bodii, Salmonella paratyphi, Pseudomonas aeruginosa and Klebsiella pneumonia (Table 1). We observed higher activity for G. edulis extract than S. aureus extract [12]. Yet it was inactive for Sporotrichum schenckii, Candida albicans and Cryptococcus neoformans [75]. In the present investigation, the chemical compounds isolated from the species were steroids (carotenoids, β-cryptoxanthin and β-carotene) [118] and carbohydrates [84,85,119] (Figure 4).

Figure 4.

Chemical structure of the steroids isolated from G. edulis.

Mahasneh et al. (1995) demonstrated activity of organic extracts from algae against multi-resistant bacteria to antibiotics [120]. Ethanol extract from G. debilis showed antibacterial activity against S. aureus but was inactive against Mycobacterium smegmatis [92].

95% ethanol extract from whole dried G. cervicornis algae was active against S. aureus at a concentration of 5.0 mg/mL [89]. Methanol extract from fresh G. corticata was active against Bacillus subtilis, Bacillus megaterium, S. aureus and Streptococcus viridians [91].

G. corticata and G. pygmea did not inhibit the growth of Aspergillus niger, Fusarium solani, Alternaria solani, or Penicillium funiculosum [91]. Petroleum ether, chloroform and methanol extracts from this seaweed at a concentration of 1.0 μg/units proved to be inactive on the inhibition of penicillinase enzyme [87]. From this specie, stearic lipids and capric acids were isolated [121] (Figure 5).

Figure 5.

Structure of compounds found in species of Gracilaria with antifungal activity.

Ethanol extracts from G. domigensis and G. sjoestedii showed antibacterial activity against E. coli and S. aureus. Ethanol extracts from G. debilis, G. domingensis and G. sjoestedii were active against Candida albicans shown by agar plate method [92]; Chloroform, ether and methanol extracts from G. tikvahiae were inactive [93]. The growth of Neurospora crassa was not inhibited by extracts from G. sjoestedii and G. debilisi; ethanol extract from G. domigensis was active against Mycobacterium smegmatis and Neurospora crassa [92]. G. domigensis has as chemical constituents, polysaccharide CT-1 [122], palmitic acid and steroids (stigmasterol, sitosterol, campesterol, cholest-7-en-3-β-ol and brassicasterol) [52] (Figure 6).

Figure 6.

Structure of the steroids isolated from G. domingensis.

Some studies highlighting antiparasitic activity of seaweeds also were verified. 90 % ethanol extract from G. corticata and G. edulis were tested against Entamoeba histolytica and Plasmodium berghei and were not active [75].

2.8. Antivirial Activity

Extracts from G. bursa-pastoris and Gracilaria sp were inactive against the Herpes simplex 1 virus (HSV) and the human immunodeficiency virus (HIV) when evaluated in cell cultures [96]. Granin BP and citrullinyl-arginine proteins were isolated from these extracts [123,124]. Methanol extract from dried G. pacifica at a concentration of 200.0 μg/mL was active against Sindbis virus, but was not effective against H. simplex 1 when tested at a concentration of 400 μg/mL. Extracts and compounds obtained from Gracilaria sp with anti-HIV activity are also active against other retroviruses such as HSV. However, the pharmacodynamic mechanisms of the antiretroviral activity are still unknown because bioactive compounds from seaweed poorly investigated [9] (Table 1) (Figure 7).

Figure 7.

Structure of a compound found in Gracilaria sp and G. bursa-pastoris.

3. Material and Methods

In this article, some reports about bioactivity of Gracilaria algae were reviewed in the specialized literature published up to January 2011. The search was carried out using data banks such as; Biological Abstracts, AlgaeBase, SciFinder Scholar, Pubmed and NAPRALERT (acronym for Natural Products ALERT-University of Illinois in Chicago, USA).

4. Conclusions

Algae are abundant in the oceans and represent a rich source of as yet unknown secondary metabolites. In this review, we found only a few studies with complete chemical profiles and pharmacological potential of the Gracilaria species. Most studies raised concerns about antimicrobial activity against Staphylococcus, Streptococcus, Candida and Herpes genus. Others referenced the cytotoxicity bioassays in which these algae species were not active, but they produce various types of prostaglandins and others substances that can be toxic to humans such as gastrointestinal disorders and lethality caused by G. verrucosa and G. edulis, respectively. To research new drugs it is necessary to evaluate other bioassay models to preserve the safety, efficacy and quality of the end products. In Brazil, there is a great need for toxicological, pharmacological, preclinical and clinical studies, as recommended by the RDC 48/2004.

Finally, we conclude that algae of the Gracilaria genus are a potential source for synthesis of new natural medicines. It is important to taxonomically classify and standardize extractions, while identifying the active compounds to attenuate possible environmental interference that could undermine the pharmacochemical profile, and thus generate different pharmacologic effects. In addition, it is important to sensitize corporate researchers and financial agencies to support this cause.