DNA sequence and chemical assessment of Thai tamarind cultivars with laxative activity

Tamarind has long been used, especially, as mild laxative in traditional medicine worldwide [1]. In Thailand, there are different tamarind cultivars of „Tamarindus indica L.“. This studie aimed to identify tamarind cultivars with laxative activity cultivated in Thailand. DNA sequence of rbcL gene of each cultivar was used to correlate with organic acids contents in tamarind pulps [2]. Sweet-type of Tamarind cultivars, i.e. „Srichomphu“, „Khanti“ and sour-type „Priao-yak“ from Phetchabun province were studied. Gene rbcL in „Srichomphu“ and „Khanti“ was found to composed of 1,428 bp, where only part of rbcL gene in „Priao-yak“, 1,398 bp was sequenced. The sequence of 1,368 bp in rbcL gene of all three cultivars were analyzed and compared with rbcL gene of T. indica (accession no. Z70160), 24 base-substitutions were found and dendrogram was constructed using UPGMA method. „Srichomphu“ and „Khanti“, both are sweet tamarind belonging to first group; „Priao-yak“ is sour tamarind belonging to second group. Organic acids, laxative active component, were quantified by HPLC [3]. Tartaric, malic and citric acids were the major organic acids in tamarind. Higher content of tartaric acid (p<0.05) was found in „Priao-yak“ (18.102±0.134%) >„Khanti“ (2.134±0.117%) >„Srichomphu“ (1.628±0.117%). Malic and citric acids contents in Khanti“ (1.837±0.015% and 0.652±0.014%, respectively) and „Srichomphu“ (1.888±0.057% and 0.631±0.030%, respectively) of sweet type were not significantly different (p>0.05). However, these values were higher than those of „Priao-yak“ (0.591±0.034% and 0.217±0.003%) of sour type (p<0.05). Identification of tamarind cultivars by rbcL gene sequences showed correlation with chemical assessment. Combination of molecular genetic and chemical assessment can be used in characterization and identification of tamarind cultivars.

Acknowledgements: We thank the Faculty of Pharmaceutical Sciences and Post Graduated Research Fund, Chulalongkorn University.

References: 1. Gunasena, H.P.M., Hughes, A. (2000) Tamarind: Tamarindus indica L. Redwood Books. Wiltshire. 2. Xai, Q. et al. (2005)J. Agric. Food Chem. 53: 6019–6026. 3. Zhanguo, C., Juiru, L. (2002)J. Chromatogr. Sci. 40: 35–39.