Assessment of the phenolic content and free radical scavenging capacity of extracts obtained from the pericarp of Garcinia mangostana L.

The pericarp of Garcinia mangostana L. is popularly used as a food supplement due to its high amount of phenolic compounds i.e., xanthones, flavonoids and tannins which promote high free radical scavenging activity [1]. This work was designed to examine the amount of phenolic constituents and the free radical scavenging capacity of extracts obtained from the pericarp of G. mangostana collected from 15 different locations in Thailand. The 95% ethanolic extracts were prepared by Soxhlet extraction. The average content of total phenolic compounds, total tannins and total flavonoids per 100 grams of extract in all samples were found to be 22.33±3.25g of gallic acid equivalent, 36.38±8.46g of tannic acid equivalent, and 4.13±1.10g of quercetin equivalents evaluated using Folin-Ciocalteu procedure, protein precipitation method, and aluminium colorimetric method, respectively. The average EC₅₀ of all extracts was found to be 17.59±5.69µg/mL determined by the DPPH scavenging method. The regression analysis between the amount of total phenolics and total tannins in the extracts exhibited a high positive relationship (r=0.9302), while the correlation coefficient between antiradical activity (1/EC₅₀) and the content of total phenolics and total tannins of all ethanolic extracts were both higher than 0.8, indicating a significant positive relationship between these parameters. Therefore, phenolic compounds and tannins seem to play an important role as free radical scavengers in pericarp extracts of G. mangostana.

Acknowledgements: This study was granted by Mahidol University Research Fund.

References: 1. Pothitirat, W. et al. (2009) Fitoterapia 80: 442–447.