In vitroantioxidant activity, lipoxygenase, cyclooxygenase-2 inhibition and Dna protection properties of memecylon species

Traditionally several species of Memecylon are used to cure skin problems. However, scientific validation of the plant as a modern medicine is lacking. Therefore, in the present study methanolic extracts of three species of Memecylon i.e., M. umbellatum, M. talbotianum and M. malabaricum were assessed for their antioxidant, anti-microbial, DNA protection capacities, 5-lipoxygenase and human cyclooxygenase (COX-2) inhibition. Methods: 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and 2,2�-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) ABTS radical scavenging capacities for extracts in dose range of 50 ìg/mL - 10 mg/mL were measured. 15-Lipoxygenase inhibition for these extracts at 10 - 200 ìg/mL dose was studied. Human cyclooxygenase-2 was recorded for doses 10 and 50 ìg/mL. DNA-nicking assay at 10 ìg was recorded. Cell cytotoxicity was recorded by colorimetric MTT assay using doxorubicin as control for extracts (50 - 500 ìg/mL). Results: The IC50 values for scavenging the DPPH radical ranged from 0.11 to 0.17 mg/mL and those for the ABTS radical cation from 2.1 to 3.7 mg/mL for the extracts. M. malabaricum leaf extract exhibited highest lipoxygenase inhibition capacity with an IC50 value of 29.87 ìg/mL. It also inhibited human COX-2 (80.6 at 50 ìg/mL). Methanolic leaf extracts could prevent DNA nicking by hydroxyl radicals, produced in the Fenton reaction. M. malabaricum leaf extracts inhibited growth of Klebsiella pneumonia, Staphylococcus aureus and Escherichia coli. Conclusion: This study forms initial screening of these plants with further studies directed towards identification of bioactive molecules as potential lead candidates