Anti-inflammatory activity of propolis extract from the stingless bee, Tetragonula pagdeni, in mangosteen orchard

Abstract

In Thailand, Tetragonula pagdeni (TP) Schwarz is one of the most common and abundantly cultured stingless bee species in mangosteen orchards. The propolis extract of TP has been used as a traditional medicine to treat inflammation. TP propolis extract also exhibited antioxidant, antiproliferative, and antimicrobial properties in scientific reports. However, the anti-inflammatory effect of TP propolis extract has been limited. Thus, this study aims to evaluate the anti-inflammatory and antioxidant effects of TP propolis extract through alteration of mRNA expression of genes involved in inflammatory processes, including cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and cytokines (e.g., tumor necrosis factor-α [TNF-α], interleukin-6 [IL-6], and interleukin-10 [IL-10]). High-performance liquid chromatography (HPLC) analysis was used to quantify the amount of major compounds, α-and γ-mangostin. TP propolis extract suppressed mRNA levels of COX-2, iNOS, TNF-α, and IL-10 in lipopolysaccharide-stimulated RAW 264.7 mouse macrophages and had no effect on IL-6 expression. HPLC quantification of α-and γ-mangostin yielded values of 36 and 34 μg/g extract, respectively. Therefore, we herein demonstrate that TP propolis extract exhibited an anti-inflammatory effect associated with the downregulation of genes involved in the inflammatory cascade. These findings suggest that TP propolis extract is a promising candidate as a nutraceutical or pharmaceutical product to relieve inflammation.