Antioxidant activity and phenolic content of different parts of Orthosiphon stamineus grown under different light intensities

Abstract

Orthosiphon stamineus is an important medicinal plant in South-East Asia. Although already widely cultivated, the influence of growing conditions, especially light intensity, on the antioxidant property of O. stamineus is still unknown. Thus, the objective of this study was to determine the antioxidant activity and phenolic content of different plant parts of O. stamineus and to propose the best environment condition for its cultivation. The leaves, stems and roots of O. stamineus treated in open environment were extracted with methanol for 4 hours in a shaking water bath at 40°C. Total phenolic content (TPC) and antioxidant activity were determined using Folin-Ciocalteu and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods respectively. In the first part of the experiment, only seedlings grown in the open environment were used. TPC was higher in leaves (230 mg gallic acid g -1 dry weight) compared with stems and roots (160 and 140 mg gallic acid g -1 dry weight respectively). However, antioxidant activity was lower in leaves (78.43%) than stems (80.66%) and roots (80.26%). By selecting leaves as the main part to study, O. stamineus grown under shaded treatment (50 and 70% shaded) as well as open environment were harvested to determine their TPC and antioxidant activities. It was observed that TPC in O. stamineus leaves grown in open environment was highest (230 mg gallic acid g -1 dry weight) compared with shade-grown seedlings. Similarly, antioxidant activity was also highest in seedlings grown in open environment (80.02%) compared with in shade (50% = 77.72%, 70% = 74.37%)