Determination of vitamin C and selected low molecular weight organic acids in aqueous extract of mulberry leaves used as dietary supplements

Abstract

Some scientific reports indicate the possibility of using different parts of mulberry (Morus alba L.) as the source of bioactive compounds to prevent type 2 diabetes. The aim of the present study was to determine the content of vit. C (ascorbic acid) and four different low molecular weight organic acids (citric, malic, oxalic, tartaric) in aqueous extracts made from the two kinds of dietary supplements: 1) containing 100% of M. alba leaf (coded as SICOM) and 2) containing admixture of mulberry leaves and other medicinal herbs (MUCOM). The content of vitamin C was determined by Tillmans method, oxalic acid - by manganometric titration, tartaric acid - by colorimetric procedure, citric and malic acid by enzymatic assays. Total acidity (expressed as content of citric acid) was determined by potentiometric titration. The average content of vitamin C in aqueous extracts of SICOM was found as 0.30 mg/100 mL, while the concentration of individual acids were found to be in range: oxalic 12.66-32.34 mg/100 mL, tartaric 14.18-26.29 mg/100 mL, citric 9.74-19.99 mg/100 mL, malic 4.52-5.23 mg/100 mL. Aqueous extracts prepared from SICOM containing coarse powder of mulberry leaves indicated the highest content of vitamin C and tartaric acid, respectively, 0.34 and 26.29 mg/100 mL, while the content of citric acid was the lowest (9.74 mg/100 mL). The results of chemometric analysis with PCA method showed that measured profile of vitamin C and the four low molecular weight organic acids could be used for superior differentiation of aqueous extracts obtained from SICOM and MUCOM dietary supplements, as well as enabling to distinguish such extracts prepared from the fine and coarse powdered mulberry leaves in these supplements.