HPLC, NMR based chemical profiling and biological characterisation of Indian propolis

The present study aimed to investigate chemical profile, antioxidant and antimicrobial activities of Indian Melifera propolis (IMP) samples collected from 13 different states. Chemical characterisation of ethanolic extracts of IMP (EEMP) samples was carried out by using HPLC and ¹HNMR spectroscopy. The antioxidant activity of EEMP samples was measured by DPPH, ABTS, and FRAP assay. Moreover, the antimicrobial activity of each EEMP sample tested against bacteria and yeast using a 96 well plate microdilution method. All EEMP samples had remarkable antioxidant and antimicrobial activities. The antioxidant potential of EEMP samples found to have a moderate positive correlation with their total phenolics and flavonoids content. Majority of EEMP samples had a minimum inhibitory concentration (MIC) ≤1mg/mL against Staphylococcus aureus. Chemometric analysis of ¹HNMR data indicated that brown, green, green-brown, red and red-brown coloured IMP samples were chemically distinct from each other, and showed two separate clusters for northern and southern states propolis samples. HPLC analysis confirmed phenethyl caffeate was most common and abundant compound in IMP samples among studied compounds. In conclusion, this study may be helpful for defining the quality of IMP as a raw material, and also in finished food and health care products.