Pharmacognostic specifications and quantitative analyses of (+)-catechin and (-)-epicatechin in Thai crude drugs under the name of Si-Siad

Abstract

Pharmacognostic specifications, antioxidant activities, total phenolic, non-tannin phenolic, and total tannin contents of Thai crude drugs under the name of Si-Siad from various sources throughout Thailand were investigated. A simple and reliable method to determine (+)-catechin and (-)-epicatechin contents was performed by high performance liquid chromatography (HPLC). Macroscopic evaluations of three plants were illustrated as whole plant drawing. Microscopic evaluation of Pentace burmanica Kurz stem bark powders showed fragment of fiber, resin masses, tannin masses, starch grain, calcium oxalate crystals, and fragment of parenchyma. The physico-chemical of Acacia catechu (Linn.f.) Wild. water extracts and Uncaria gambir (Hunter) Roxb. water extracts were divided into two classes of purity according to ash contents. Some of Acacia catechu water extracts and all of Uncaria gambir water extracts and Pentace burmanica stem bark extracts exhibited good antioxidant activities and showed high contents of total phenolics and non-tannin phenolics. The results demonstrated that greater amount of phenolic contents lead to more potent antioxidant effects. Moreover, the different sources of the Si-Siad samples showed the variation in both antioxidant activities and phenolic contents. Some of Acacia catechu water extract samples consisted of (+)-catechin and (-)-epicatechin as major compounds. (+)-Catechin was the main compound of Uncaria gambir water extracts; whereas (-)-epicatechin was the main compound of Pentace burmanica stem bark extracts. The validation parameters were investigated according to ICH guideline. The validation of the method revealed that the HPLC method showed good sensitivity and accuracy for (+)-catechin and (-)-epicatechin quantitations in Thai crude drugs under the name of Si-Siad. Hence, this HPLC method could be applied to determine (+)-catechin and (-)-epicatechin in plant materials.