Determination of antioxidant property from some medicinal plant extracts from Thailand
The evaluation of antioxidant property, total phenolic compounds and pigment content of 8 medicinal plants including: Gynostemma pentaphyllum Thunb., Camellia sinensis Ktze., Cymbopogon citratus Stapf., Centella asiatica (L.) Urban., Andrographis paniculata (Burm.) Wall. ex Nees, Thunbergia laurifolia Lindl., Murdania loriformis (Hassk.) Rolla Rao et Kammathy and Acanthus ebracteatus Vahl., was performed using 95% methanol as a solvent. C. sinensis methanolic extract showed the highest antioxidant activity with 0.34 μg/ml IC50 followed by the extract of C. asiatica and G. pentaphyllum, respectively. The extract of A. paniculata had the highest chlorophyll a yield. C. sinensis extract had the highest chlorophyll b content. While, the carotenoid constituent can be determined only in G. pentaphyllum methanolic extract. However, the highest level of total pigment was in C. sinensis extract. Correlation analysis found a statistically significant relationship with an exponential pattern between the amount of total phenolic compounds and the antioxidant property at correlation level was 0.9687. On the other hand, the total pigment yield did not have a correlation with antioxidant activity.
Key words: Pigment, phenolic compound, antioxidant, medicinal plant.