Chemical profile and antidiabetic activity of raw and polyphenol extracts of Malaysian honey

High amount of carbohydrates present in honey poses a challenge for identifying specific phenolics and flavonoids, as these bioactive compounds are typically present in lower concentrations. Therefore, the present work aimed to investigate the chemical profiles of two Malaysian honey types, Gelam and Tualang, including their raw and polyphenol extracts. The present work also evaluated the antidiabetic property of the raw and polyphenol extracts via α-glucosidase inhibitory activity. The 1H NMR metabolomics successfully differentiated between the raw and polyphenol extracts of Gelam, Tualang, and Manuka honey. A total of 18 metabolites, including phenolics/flavonoids, carbohydrates, amino acids, and organic acids were responsible for the separation of raw and polyphenol extracts of honey samples. The principal component analysis (PCA) loadings plot showed signals in the aromatic region of polyphenol extracts, potentially belonging to phenolics and flavonoids. HPLC analysis confirmed the presence of kaempferol, luteolin, isorhamnetin, hesperetin, chlorogenic acid, naringenin, ferulic acid, sinapic acid, and quercetin in honey samples. The results indicated that Gelam honey had higher total phenolic and flavonoid contents than Tualang honey. The α-glucosidase inhibitory activity results revealed that the raw honey of Gelam, Tualang, and Manuka exhibited a higher percentage of inhibition at the concentration of 500 μg/mL (52.58 ± 2.43%, 39.03 ± 3.47%, and 50.54 ± 0.23%, respectively) compared to the polyphenol extracts (0.57 ± 0.05 - 1.09 ± 0.09%). The antidiabetic mechanisms of the polyphenols towards in silico molecular docking revealed rutin having the highest binding affinity (-10.1 kcal/mol) compared to other compounds. Although phenolics and flavonoids contribute to antidiabetic activity, results obtained in the present work indicated that other metabolites, such as amino acids and organic acids, were mainly responsible for the antidiabetic activity of Gelam and Tualang honey. The present work provided important information on the chemical profile and antidiabetic activity of Malaysian honey.