Antioxidative Potentials of Some Thai Indigenous Vegetables and Fruits

Abstract

Eleven Thai indigenous vegetables and fruits, commonly consumed in the Northeast region of Thailand were purchased at a local market, Surnin Province, Thailand. Edible parts such as buds (young leaves and shoots), leaves roots, fruits or flowers were used for analysis. Total phenolic contens were determined using Folin-Ciocalteu method and the antioxidant activity was assessed the free radical scavenging using two methods; ABTS and DPPH assays. THe activity was expressed as Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2 - carboxylic acid) equivalent antioxidant capacity (TEAC) and the amount of plant materials necessary to decrease DPPH (2,2 - Diphenyl -1- picrylhydrazyl) radical concentrate by 50% (EC₅₀) respectivey. Thai indigenous plants studied are a tich source of antioxidants, The phenolic contents ranged from 42.6 to 3434.6 mg GAE/g dry matter (DM) or 379.1 to 55985.4 mg GAE/100g fresh weight (FW) of plant materials. THe high leel contents (>200 mg GAE/g DM) consisted of buds of Careya sphaerica, Cratoxylum formosum, Syzygium gratum, Azadirachta indica Juss var Siamensis and fruit of Phyllanthus embilca. The moderate level (100-500 mg GAE/g DM) was found in the Musa sapientum flower, Acacia pennat buds, Eugenia cumini and Lepisanthes rubiginosa fruits. The low level (<100mg GAE/g DM) comprised Centella asiatica and Artocarpus lakoocha buds. The antioxidative potentials were correlated to the total phenolics compounds of plants, the higher amounts of phenolics compounds contained, the higher antioxidative capacity detected. The antioxidant activity ranged from 21.66 to 4085.55 μM TEAC/g DM. The high capacities to scavenge ABTS⁺ radicals were found in Careya sphaerica, Syzygium gratum, Phyllanthus embilica and Azadirachta indica Juss var Siamensis Valeton and Cratoxylum formosum (4085.55, 2827.46, 2234.30, 2059.57 and 1012.91 μM TEAC/g DM respectively). The highest antioxidant capacity determined by DPPH method was also found in these plants. The values of EC₅₀ were 0.14, 0.28, 0.21, 0.40 and 0.43 mg DM/mL respectively. The low antioxidant activity was detected in Artocarpus lakoocha, Centella asiatica and Acacia pennata (34.39, 21.66 and 40.55 μM TEAC/g DM; and EC₅₀ values of 30.42, 45.00 and 32.97 mg DM/mL respectively).