Antioxidant and antibacterial properties of the leaves and stems of Premna microphylla

Premna microphylla is widely used in the Chinese folk medicine for the treatment of different infections diseases. In this study, ascorbic acid and β-carotene contents of the fresh P. microphylla leaves and stems were determined byspectrophotometric method. In addition, the antioxidant and antibacterial activities and phenolic contents of the methanol extracts of the dry leaves and stems were evaluated using in vitro standard methods. The results showed that ascorbic acid and β-carotene contents of the leaves and stems were both considerable. The antioxidant activities of the stem extract of P. microphylla as determined by the total phenolics, flavonoids, and ferrous reducing antioxidant property methods were significantly higher than that of leaves. On the other hand, the leaf extract of the plant had higher level of proanthocyanidins. Moreover, the leaf extract also had higher radical scavenging activity than the stem as shown in 1,1-Diphenyl-2-picrylhydrazyl assay. The antibacterial assay showed that the methanol extracts from the leaves and stems had significant activity against both Gram-positive and Gram-negative bacteria. The activity of the leaf extract was more pronounced on several bacterial species, compared with that of stem extract on three bacterial species with the minimum inhibitory concentrations of 10 mg/ml. The results obtained in this study suggested P. microphylla could be a potential good candidate for functional foods as well as pharmaceutical plant-based products.   Key words: Premna microphylla, antioxidant, antibacterial, methanol extract.