Quantification of bioactive constituents and determination of free radical scavenging activity in mangosteen fruit rind extracts

The pericarp of mangosteen (Garcinia mangostana L., Guttiferae) has been used as dyeing agent and traditional medicine, e.g. as antidiarrhoea and antidysentery agent and for the treatment of wounds [1]. In this study, the content of bioactive constituents and free radical scavenging activity of unripe and ripe fruit rinds of G. mangostana were determined and compared. Ethanolic extracts of the unripe and ripe fruit rinds were examined for the content of total phenolic compounds, total flavonoids, and total tannins using Folin-Ciocalteu procedure [2], aluminium chloride colorimetric method [3], and protein precipitation method [4], respectively. The results showed that the content of total phenolic compounds (42.57±0.11g GAE/100g extract) and total tannins (51.25±0.20g TAE/100g extract) in unripe fruit rind extract were higher than in the ripe fruit rind extract, while the highest content of total flavonoids was found in the extract of ripe fruit rind (4.08±0.07g QE/100g extract). Validated analytical methods, i.e., TLC-densitometry and HPLC, were developed for determination of α-mangostin contents in unripe and ripe fruit rinds of G. mangostana. The highest content of α-mangostin was found in the ripe fruit rind extract (16.65±0.38% w/w by TLC-densitometry, and 13.63±0.06% w/w by HPLC). Free radical scavenging activity was evaluated from EC₅₀ value using DPPH scavenging method. The unripe fruit rind extract gave higher free radical scavenging activity (EC₅₀, 5.56±0.12µg/ml). This study demonstrates differences in the content of chemical components and free radical scavenging activity between unripe and ripe fruit rinds of G. mangostana. This work also compared the content of α-mangostin in the fruit rind extracts using different analytical methods; TLC-densitometry, and HPLC. These methods are useful for quantitative analysis of α-mangostin in raw materials, extracts, pharmaceuticals, and cosmetic products from this plant.

Acknowledgement:: This study was supported by a research grant from Mahidol University, Bangkok, Thailand.

References: [1] Saralamp, P., Chuakul W., et al. (1996) Medicinal Plants in Thailand. Amarin printing and publishing Public Co., Ltd. Bangkok. [2] Kim, KH. et al. (2006) Food Chem 95: 466–473. [3] Meda, A. et al. (2005) Food Chem 91: 571–577. [4] Hagerman, AE. and Butler, LG. (1978) J Agric Food Chem 26(4): 809–812.