A new flavonoid isolated from Indigofera daleoides Mathabe M.C.1, Hussein A.A.2,†, Lall N.2,*, Nikolova R.V.1, Basson A.E.2,‡, Meyer J.J.M.2 1Department of Botany, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa. 2Department of Botany, University of Pretoria, Pretoria 0001, South Africa. *Corresponding author: Namrita Lall, E-mail: namrita.lall@up.ac.za
†Present address: Pharmacognosy and Chemistry of Medicinal Plants Laborotory, National Research Center, Dokki, Cairo, Eqypt. ‡Present address: National Institute for Communicable Diseases, Private Bag X4, 2131 Sandringham, South Africa. Abstract Indigofera daleoides Benth. ex Harv. & Sond. (Fabaceae) is used by traditional healers in Limpopo Province for treatment of diarrhoea. The bioassay-guided fractionation of the ethylacetate extract from I. daleoides led to the isolation of two pure compounds which were identified as compound 1 (6,2-O-[3-nitropropanoyl-β-D-glucopyranose]) and compound 2 with a novel skeleton (6,3′,4′-trihydroxyflavan 5′-O-glucopyranoside). These compounds were isolated for the first time from I. daleoides. Isolated compounds were tested for antibacterial and cytotoxic activities in vitro using micro dilution method and sodium-2,3-bis-[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) assay, respectively. The results showed that compound 2 (flavonoid), isolated from I. daleoides, exhibited the highest antibacterial activity against S. aureus, S. typhy, V. cholera, E. coli and S. dysentery with MIC values ranging between 25–50 μg/ml. Compound 1 (nitrocompound) was found to be less active than compound 2 (flavonoid) against most of the bacteria tested. Staphylococcus aureus had higher susceptibility to compound 2 (flavonoid) as compared to the other bacteria tested. Compound 1 (nitrocompound) and 2 (flavonoid) isolated from I. daleoides had relatively high fifty per cent inhibitory concentration (IC50 values) (349.4 and 364.5 μg/ml, respectively) as compared to the crude extract (IC50 254 μg/ml), thus suggesting these compounds are less cytotoxic to Vero cells than the crude ethanol extract. The results of this study suggest possible antidiarrhoeal potential of these compounds, especially compound 2 (flavonoid) from I. daleoides which need to be further investigated. This is the first report on the antibacterial activity and cytotoxicity of purified compounds from I. daleoides. Top Keywords Indigofera daleoides, Euphorbiaceae, antibacterial activity, cytotoxicity, flavonoids, nitro compounds. Top |