Identification of Phenolic Compounds in Melastoma malabathricum (L.) Extract by HPTLC Technique and their Food Pathogenic Bacteria Activities

Abstract

Melastoma malabathricum is a native plant found in the Southern region, Thailand. It has been used to treat and disinfect. Thus, this study was carried out to identify and determine the contents of five phenolic compounds such as catechin, gallic acid, rutin, luteolin and quercetin in an acetone extract of Melastoma malabathricum from ultrasonication extraction. By extracting parts of fruit, leaf, stem and root; subjected to HPTLC analysis it was simple, economical, rapid and eco-friendly technique followed by small amount of waste produced, to quantify the contents of five phenolic constituents of biological interest. Results with the standard curve correlated between the peak area of absorbance at the wavelengths of 254 nm and 366 nm and the concentration of the standard solution, which were analyzed with the same HPTLC 60F254 silica gel plate as the extract. The result showed the linear calibration curve (r > 0.99), the analysis range was in the range of 100 - 2000 ng/band. The fruit was contained the most active compounds: catechin (0.027%), gallic acid (0.034%), luteolin (0.017%) and quercetin (0.020%). The other parts were found only two active components: 0.011-0.049%. In addition, the inhibitory effect of the extracts on the three bacteria strains; S. aureus, B. cereus and E. coli, was determined by agar well diffusion method. It was found that the stem and root extract were able to inhibit only S. aureus. From the results of the studies, Melastoma malabathricum is useful as a food supplement and it may improve other food product developments.