Comparative study of bioactive compounds and biological activities among Thai monofloral honeys from different floral origins

Abstract The study compares the biological potential of six varieties of honey from different floral origins in Thailand, including longan ( Dimocarpus longan Lour.), premium longan (raw honey derived from Dimocarpus longan Lour.), Siam weed ( Chromolaena odorata ), lychee ( Litchi chinensis Sonn. ), coffee ( Coffea arabica L.), and Manuka ( Leptospermum scoparium ). Total phenolic content (TPC) and total flavonoid content (TFC) were determined, followed by the evaluation of antioxidant activities using ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ascorbic acid equivalent antioxidant capacity (AEAC) assays. Quantitative analysis of phenolic and flavonoid compounds was performed using high-performance liquid chromatography (HPLC), with compound identification based on retention times of authentic standards. Antimicrobial activity, expressed as minimum inhibitory concentration (MIC), and basic physicochemical properties were also evaluated. Multivariate analyses, including principal component analysis (PCA) and Pearson correlation were applied to link the biochemical composition of honeys with biological activities. Manuka and premium longan honeys exhibited the highest phenolic and flavonoid levels and strong antioxidant capacities. Major compounds, including gallic acid, caffeic acid, quercetin, and catechin, showed significant correlations with TPC, TFC, and both antioxidant and antimicrobial activities. PCA grouped Manuka and premium longan honeys in a high-bioactivity cluster, closely associated with antioxidant variables and low MIC values, particularly against Staphylococcus aureus (7.5% w/v). Lychee honey showed high flavonoid content but limited antimicrobial activity, while coffee and conventional longan honeys displayed moderate activities. In contrast, Siam weed honey exhibited the lowest bioactive levels, consistent with its weak antioxidant and antimicrobial properties. Multivariate analyses confirmed that phenolics and flavonoids are the main drivers of honey bioactivities. These findings highlight Thai premium longan honey as a promising bioresource for functional food and cosmeceutical development, supporting its potential to enhance local economic value.