Antioxidant and aldose reductase inhibitory capacities of Tephrosia humilis aerial parts' extracts
Tephrosia humilis (Leguminosae), is a tropical shrub endemic in central Africa. Species of this genus are used in traditional remedies as antimicrobial, tonic, diuretic, anthelminthic, blood purifier etc [1,2]. Phytochemical analysis of other Tephrosia species resulted in the isolation of coumarins, and several flavonoids [3–9]. The aim of this study was the evaluation of the antioxidant capacity of several plant extracts of Tephrosia humilis (DPPH assay and Co(II)/EDTA -induced luminol chemiluminescence test), as well as their ability to inhibit the aldose reductase enzyme (AR, ALR2, E.C. 126.96.36.199), indicating a potential of this plant to act against the long term diabetic complications [10,11]. After defatting, plant material was extracted in a soxhlet apparatus with methanol and the dry remaining was partitioned with solvents of increasing polarity, giving five different fractions (diethyl ether, ethyl acetate, ethyl acetate residue, n-butanol, water). Antioxidant results according to both tests proved the good antioxidant capacity of the ethyl acetate fraction in comparison to the standards used (trolox and quercetin) . While according to the CL test all other fractions showed low hydroxyl radical scavenging ability, DPPH test results proved that the n-butanolic and ethyl acetate residue fractions are also effective radical scavengers. As about the ALR2 inhibition, all fractions, except the aqueous, were strong inhibitors at the concentration of 25µg/ml in comparison to sorbinil. The n-butanolic and the ethyl acetate fractions inhibited the enzyme above 75%. This research work proves in vitro the good antioxidant capacity of Tephrosia humilis extracts, as well as their strong inhibitory activity against ALR2 enzyme.
References: 1. Bashir, A.K. et al. (1992) Fitoterapia 63: 371. 2. Kole, RK et al. (1992)J. Agric. Food Chem. 40: 1208–1210. 3. Ahmad, S. (1986) Phytochem. 25: 955–958. 4. Menichini, F. et al. (1982) Planta Med. 45: 243. 5. Rajani, P. et al. (1988) Phytochem. 27: 648–649. 6. Rao, E.V. et al. (1984) Phytochem. 23: 1493–1501. 7. Venkata, R. et al. (1979) Phytochem. 18: 1581–1582. 8. Hussaini, F.A. et al. (1986) Planta Med. 52: 220–221. 9. Gupta, R.K. et al. (1980) Phytochem. 19: 1264. 10. Nicolaou, I. et al. (2004)J. Med. Chem. 47: 2706–2709. 11. Matthew, J. et al. (2002)J Amer Med Assoc 288: 2579–2582. 12. Termentzi, A. et al. (2006) Food Chem. 98: 599–608