Antibacterial and antioxidant activities of four kaempferol methyl ethers isolated from Dodonaea viscosa Jacq. var . angustifolia leaf extracts

J.N Eloff,M.A Aderogba,L.S Teffo

doi:10.1016/j.sajb.2009.06.010

Abstract

Fractionation of dichloromethane and acetone fractions obtained by serial extraction from the leaf powder of Dodonaea viscosa Jacq. var. angustifolia (Sapindaceae) resulted in the isolation of four kaempferol methyl ethers. The compounds were identified by spectral data ( 1H NMR, 13C NMR and MS) as: 3, 5, 7-trihydroxy-4'-methoxyflavone ( 1); 5, 7, 4'-trihydroxy-3, 6-dimethoxyflavone ( 2); 5, 7-dihydroxy-3, 6, 4'-trimethoxyflavone (santin) ( 3); and 5-hydroxy -3, 7, 4'-trimethoxyflavone ( 4) together with 3,4',5,7-tetrahydroxy flavone (kaempferol) ( 5). Antioxidant potential of the compounds was evaluated using a DPPH spectrophotometric assay, while antibacterial activity was determined using a serial dilution microplate technique. The isolates demonstrated varying degrees of antioxidant and antibacterial activities. Of all the compounds investigated, compounds 1 and 5 demonstrated some antioxidant activity (EC 50 = 75.49 ± 1.76 µM and 35.06 ± 0.85 respectively) but lower than l-ascorbic acid (EC 50 = 13.55 ± 0.28 µM) used as a standard antioxidant agent. The minimum inhibitory concentration (MIC) of isolated compounds against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa varied from 16 µg/ml to more than 250 µg/ml. Some structure activity relationships could be established for these compounds.

Highlights

Teffo et al / South African Journal of Botany xx (2009) xx–xxx antibacterial compounds could be sequestered by the insect (Teffo, 2006; Teffo et al, 2007), There has been some reports on the antibacterial activity of D. viscosa extracts but we found no publication on the compounds responsible for the antibacterial and antioxidant activities of this widely used medicinal plant
AA% = 100−f1⁄2ðAbssample−AbsblankÞ × 100=Abscontrolg (Abssample is the absorbance of the sample, Absblank is the absorbance of the blank and Abscontrol is the absorbance of the control)
EC50 is the concentration of the test sample leading to a 50% inhibition of the DPPH free radicals

Summary

Introduction

Dodonaea viscosa Jacq. var. angustifolia (Sapindaceae) is a medicinal plant used in folk medicine to treat various ailments; the leaves have traditionally been administered to treat the following: sore throat, wounds, fever (Jansen, 1981); piles (Tadese, 1994); fever, malaria, angina, cold, arthritis, sinusitis flu (Lemordant, 1971); and boils, dressing for skin diseases of the head and face (Sandhya et al, 2006; Abate, 1989). Getie et al (2003) reported that a methanol leaf extract of D. viscosa from Ethiopia demonstrated antibacterial activity against Staphylococcus aureus, Streptococcus pyogenes and Corynebacterium diphtheriae and exhibited antiviral activity against Coxsackie virus B3 and Influenza A virus. Getie et al (2003) reported that a methanol leaf extract of D. viscosa from Ethiopia demonstrated antibacterial activity against Staphylococcus aureus, Streptococcus pyogenes and Corynebacterium diphtheriae and exhibited antiviral activity against Coxsackie virus B3 and Influenza A virus. Their quantitative data were obtained by using the agar diffusion. This method is not useful to quantify antimicrobial activity of plant extracts for comparative purposes. We decided to reinvestigate the antibacterial activity of D. viscosa leaf extracted with solvents of various polarities by using a microplate serial dilution assay (Eloff, 1998).that would provide MIC data

Methods

Results

Conclusion