Key Organic Acids in Indigenous Plants in Thailand

Abstract

Organic acids had various health benefits such as citric acid can inhibit stone formation and break up beginning of small kidney stone. On the other hand, some organic acid showed negative health effect s such as oxalic acid acts as anti-nutrients and can cause kidney stone. Most of Thai indigenous plants had sour taste; however general people believed that sour taste of plants could contain high ascorbic acid. In addition, there is limit report of organic acids and ascorbic acid in Thai indigenous plants. This study determined organic acids, ascorbic acid, pH, and total acidity in indigenous plants. Forty samples of 29 types of indigenous plants were analyzed. Results showed that young leaves of Cratoxylum formosum found the highest succinic acid (2454 ± 91 mg/100g fresh weight, FW) and high ascorbic acid (142 ± 35 mg/100g FW). Fruits of Antidesma ghaesembilla had high citric acid levels (5161 ± 109 mg/100g FW) but contained very low ascorbic acid (2 mg/100g FW). The sum of organic acids had significant and inverse correlations with pH ( r = - 0.680) and positive with total acidity ( r = 0.672) but was not significantly correlated for ascorbic acid ( r = 0.536). The sour taste of plants could derive from the sum of organic, citric, and formic acids, but not other organic and ascorbic acids. Against traditional belief, plants having a strong sour taste may not contain significantly high amounts of ascorbic acid.