Location: Natural Products Utilization ResearchTitle: Phytochemical, antimicrobial and antiplasmodial investigations of Terminalia brownii Author
Submitted to: Natural Product Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2013
Publication Date: 7/1/2013
Citation: Machumi, F., Midiwo, J.O., Jacob, M.R., Khan, S.I., Tekwani, B.L., Zhang, J., Walker, L.A., Muhammad, I. 2013. Phytochemical, antimicrobial and antiplasmodial investigations of Terminalia brownii. Natural Product Communications. 8(6):761-764. Interpretive Summary: Phytochemical analysis of the ethyl fraction of stem bark extract of an African medicinal plant Terminalia brownii Fresen. led to isolation of a new oleanane-type triterpenoid (1), along with seven known triterpenoids, namely arjunic acid (2), sericic acid (3), 23-galloylarjunic acid (4), tomentosic acid, arjungenin, sericoside and arjunglucoside I; seven ellagic acid derivatives. The isolated compounds were evaluated for their antimicrobial and antiplasmodial activities. Compounds with galloyl group (4 and 6) were found to be active against chloroquine sensitive (D6) and resistant (W2) strains of Plasmodium falciparum, whereas three ellagic acid derivatives (5-7) were found active against three species of fungi and one species of bacteria.
Technical Abstract: The stem bark of Terminalia brownii was collected from Machakos county, Kenya, in November 2011, and identified at the University Herbarium, School of Biological Sciences, University of Nairobi, where a voucher specimen (JM2011/502) was deposited. The stem bark was air dried in shade and pulverized. Dried and pulverized stem bark (0.6 Kg) was extracted by cold percolation at room temperature using 1:1 CH2Cl2/MeOH (3×XL, each 24 h), followed by 100% methanol (1×2L, 24 h). The filtrates were rotavaped and combined to give 5 g of black-brown gummy extract, which was suspended in methanol/water (2:8, 100mL) and partitioned successively with n-hexane and EtOAc (2 x 200mL each) to give 0.2 g of n-hexane extract, 2.1 g of ethyl acetate extract and 2.2 g of residual water extract. 2.0 g ethyl acetate extract was chromatographed over RP-18 silica gel (100 g, 3 x 30 cm) eluted with H2O/MeCN 8:2 (800 mL), 7:3, (1200 mL), 6:4 (600 mL), 1:1 (1000 mL), 6:4 (400 mL), 8:2 (300 mL) and 100% MeCN (1000 mL). 260 fractions of 20 mL each were collected and combined according to similarities in their TLC patterns. Repeated column chromatography and crystallization afforded the compounds in the following order: 4-(a-L-rhamnopyranosyl)ellagic acid (14.6 mg, afforded by crystallization of fractions 22-28 in MeOH/CHCl3), 3-O-methyl-4-(a-L-rhamnopyranosyl)ellagic acid (47 mg, crystallized in fractions 44-51, H2O/MeCN; 7:3), arjunglucoside I (5.7 mg, afforded by cleaning fractions 52-53 by Sephadex LH-20 CC using MeOH/CHCl3 7:3), diellagic lactone (7, 6.5 mg, precipitated in MeOH solution of fractions 54-56), sericoside (15.2 mg, obtained by sephadex LH-20 CC of fractions 61-65 with MeOH/CHCl3; 7:3), 3-O-methylellagic acid (5, 4.0 mg, obtained by sephadex LH-20 CC of fractions 61-65 with MeOH/CHCl3; 7:3), 4-O-(3´´,4´´-di-O-galloyl-a-L-rhamnopyranosyl)ellagic acid (6, 21.1 mg, afforded by sephadex LH-20 CC of fractions 77-81 with MeOH/CHCl3; 7:3), 3,3´-di-O-methylellagic acid (13 mg, crystallized in fractions 95-100, H2O/MeCN; 7:3), 3,3´4-tri-O-methylellagic acid (5.2 mg, obtained by silica gel CC of fractions 113-118 using CHCl3/MeOH; 9:1), arjugenin (14.6 mg, afforded by silica gel CC of fractions 126-130 using CHCl3/MeOH; 92:8), tomentosic acid (16.0 mg, afforded by silica gel CC of fractions 132-139 using CHCl3/MeOH; 92:8), 23-galloylarjunic acid (4, 6.5 mg, afforded by silica gel CC of fractions 126-130 using CHCl3/MeOH; 92:8), sericic acid (3, 168 mg, crystallized in fractions 144-161, H2O/MeCN; 1:1), arjunic acid (2, 6.8 mg, afforded by silica gel CC of fractions 177-194 using CHCl3/MeOH; 94:6), 3ß,24-O-ethylidenyl-2a,19a-dihydroxyolean-12-en-28-oic acid (1, 2.8 mg, afforded by silica gel CC of fractions 177-194 using CHCl3/MeOH; 94:6) and 3-O-ß-D-glucopyranosyl-ß-sitosterol (4.0 mg, afforded by silica gel CC of fractions 255-258 using CHCl3/MeOH; 93:7).