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2.2 Acacia Species
2.2.1 Ethnopharmacological Properties and Phytochemistry
Acacia arabica (Lam.) Willd. (Fam. – Mimosaceae) is used in treatment of various diseases including diabetes and skin diseases and is considered as an astringent, demulcent, aphrodisiac, anthelmintic, and antimicrobial and antidiarrheal agent, with good nutritional value in traditional medicine of India (Chopra et al. 1956; Jain et al. 1987 2005; Rajvaidhya et al. 2012), and an effective remedy for malaria, sore throat, and toothache (Joshi 2007; Kubmarawa et al. 2007). The bark decoction of Acacia catechu mixed with milk is used for cure of cold and cough, in combination with opium, which helps in curing severe diarrhea. The katha from A. catechu applied on lemon slice coated with catechu is recommended as remedy to treat (with empty stomach) piles in patients. It is also used in curing of mouth ulcers and body pains. The heartwood is boiled with water, and the prepared decoction is recommended for pregnant women to keep their body warm during cold seasons as well as to help in child delivery and milk secretion. It is also applied externally on ulcers, boils, skin eruptions, and gums as disinfectant (Chowdhury et al. 1983; Singh and Lal 2006). Acacia nilotica is therapeutically used as antiscorbutic, astringent, antioxidant, natriuretic, antispasmodic, and diuretic for intestinal pains and diarrhea, nerve stimulant, colds, congestion, coughs, dysentery, and fever (Saini 2008); the seeds have antimalarial, antidiabetic, and antihypertensive properties. The leaves and pods are an excellent fodder with anti-inflammatory, molluscicidal, and algicidal properties, while the bark is recommended for the treatment of hemorrhages, cold, diarrhea, tuberculosis, and leprosy. The quercetin 3-galactosyl and flavones are isolated from this plant species and showed antibacterial (against Bacillus subtilis, Escherichia coli, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Staphylococcus aureus bacterial species) and anti-inflammatory activities (Bashir et al. 2014; Stoh and Bagchi 2015). Acacia ataxacantha showed significant antioxidative property that could be used in pharmaceutical and food preparations (Amoussa et al. 2015).
Tannin and phlobatannin, gallic acid, protocatechuic acid, pyrocatechol, (+)-catechin, (−)-Epigallocatechin 7-gallate and (−)-epigallocatechin-5,7-digallate (Ali et al. 2012), gallic acid, ellagic acid, isoquercetin, leucocyanadin, kaempferol-7-diglucoside, glucopyranoside, rutin, derivatives of (+)-catechin-5-gallate, apigenin-6,8-bis-glucopyranoside, m-catechol and their derivatives, m-digallic acid, (+)-catechin, chlorogenic acid, gallolyated flavan-3,4-diol, robidandiol (7,3,4,5-tetrahydroxyflavan-3-4-diol), androstene steroid, D-pinitol carbohydrate, and catechin-5-galloyl ester were isolated from A. nilotica (Singh et al. 2009). The bark of this plant species contains condensed tannin and phlobatannin, gallic acid, protocatechuic acid, pyrocatechol, (+)-catechin, (−)-epigallocatechin-7-gallate, and (−)-epigallocatechin-5,7-digallate (Singh et al. 2009), (−)-epicatechin, (+)-dicatechin, quercetin, gallic acid, (+)-leucocyanidin gallate, sucrose, (+)-catechin-5-gallate (Mitra and Sundaram 2007), and kaempferol umbelliferone. The leaves, roots, seeds, bark, fruits, flowers, gum, and immature pods possessed anticancer, antimutagenic, spasmogenic, vasoconstrictor, anti-pyretic, anti-asthmatic, cytotoxic, antidiabetic, anti-platelet aggregatory, antiplasmodial, molluscicidal, antifungal, and inhibitory activities (Singh et al. 2010). Similarly, heartwood of Acacia giraffae and Acacia galpinii showed the presence of (+)-2,3-trans-3,4-trans-teracacidin (7,8,4′-trihydroxy-flavan-3,4-diol), 3-O-methyl-, 7,8-di-O-methyl-, 7,8,4′-tri-O-methylflavonol, (−)-2,3-cis-3,4-cis-melacacidin (7,8,3′,4′-tetrahydroxyflavan-3,4-diol), leueofisetinidin, (+)-catechin, (+)-2,3-trans-3,4-trans-leucofisetinidin (7,3′,4′, trihydroxyflavan-3,4-diol), trans-(+)-(leueofisetinidin-(+)-catechin) (Malan and Roux 1975; Abdel Karim et al. 2017).
The 8-methoxyflavonones including 7,8,4′-trihydroxy-3-methoxyflavone, 7,8,3′,4′-tetrahydroxy-3-methoxyflavone, 7,3′,4′-trihydroxy-3,8-dimethoxyflavone, 7,3′4′-trihydroxy-8-methoxyflavonol, fisetin, 8-methoxy-fisetin, and 7,8,4′-trihydroxyflavonol were isolated from Acacia species (Clark-Lewis and Porter 1972). The ethyl acetate fraction, (−)-ascorbic acid, 3,7,8,3′4′-pentahydroxyflavone, 3,8,3′,4′-tetrahydroxy-3-methoxyflavone, 3,4,2′,3′,4-pentahydroxy-trans-chalcone, 3,7,8,3′-tetrahydroxy-4′-methoxyflavone, and (+)-catechin from Acacia confusa showed antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) model (Wu et al. 2005). Kaempferol 3-dixyloside, kaempferol 7-glucoside, kaempferol 3,7-dirhamnoside, kaempferol 7,4′-digalactoside, myricetin 3-glucoside, myricetin 3,7-diglucoside, kaempferol 4′-galactoside, kaempferol 3-glucoside, kaempferol 3,7-diglucoside, quercetin 3-diglucoside, quercetin 3-glucoside, quercetin 3′-methyl ether, and quercetin 7-glucoside flavonoids are isolated from Acacia mangium (Umi Kalsom et al. 2001; Harborne 1971, Tindale and Roux 1975). Some triterpenoids, saponins (Mahato et al. 1992; Uniyal et al. 1992), coumarins, tannins, carbohydrates, alkaloids, and/or nitrogenous bases (Wassel et al. 1992) and cyanogenic compounds have also been reported from Acacia species (Seiger et al. 1989).
The catechin, epicatechin, epicatechin-3-O-gallate, and epigallocatechin-3-O-gallate (Shen et al. 2006), rhamnetin, 4-hydroxyphenol, 3,3′,5,5′,7-pentahydroxyflavane, fisetinidol, 5-hydroxy-2-[2-(4-hydroxyphenyl)acetyl]-3-methoxybenzoic acid, (2S,3S)-3,7,8,3′,4′-pentahydroxyflavone, (3R,4R)-3-(3,4-dihydroxyphenyl)-4-hydroxycyclohexanone and (4R)-5-(1-(3,4-dihydroxyphenyl)-3-oxobutyl)-dihydrofuran-2(3H)-one (Li et al. 2011a,b), catechin, gallic acid, and epicatechin were identified from the aqueous extract of A. catechu (Hiraganahalli et al. 2012; Sulaiman and Balachandran 2012). Twelve compounds were identified as 4-hydroxybenzoic acid, kaempferol, quercetin, 3,4′,7-trihydroxyl-3′, 5-dimethoxyflavone, catechin, epicatechin, afzelechin, epiafzelechin, mesquitol, ophioglonin, aromadendrin, and phenol from A. catechu for the first time (Li et al. 2010). A novel polyphenolic compound 6,7,8-trihydroxy-3,4′-dimethoxy dihydroxyflavone was isolated for the first time from MeOH extract of the leaves of Acacia sieberiana (Abdelhady 2013) and demonstrated antioxidant activity (Sowndhararajan et al. 2015). Three pentacyclic triterpenoids as (20R)-3-oxolupan-30-al,
