Stingless bees (Apoidea) are widely distributed and commercially cultivated in artificial hives in fruit gardens. Their propolis are commonly used in traditional medicine to treat various diseases (e.g., abscesses, inflammations, and toothaches) and as a constituent of numerous health products. Thus, this study aimed to (i) develop and validate a high-performance thin layer chromatography method for the quantitation of major active constituents (α- and γ-mangostins) in propolis produced by five stingless bee species (Tetragonula fuscobalteata Cameron, T. laeviceps Smith, T. pagdeni Schwarz, Lepidotrigona terminata Smith, and L. ventralis Smith) cultivated in Thai mangosteen orchards and (ii) determine an optimal extraction solvent. Separation was performed on a silica gel 60 F₂₅₄ plate using toluene/ethyl acetate/formic acid (8:2:0.1, v/v/v) as a mobile phase, and the developed method was validated to assure its linearity, precision, accuracy, and limits of detection/quantitation. Propolis extract from T. fuscobalteata exhibited the highest mangostin content, and acetone was shown to be more a more effective extraction solvent than dichloromethane, ethanol, or methanol. Thus, the simplicity and reliability of the developed method make it well suited for the routine analysis (e.g., for quality control) of commercial products containing stingless bee propolis.

Salak seed extract (Salacca zalacca) is known for its high antioxidant content and low caffeine levels, making it a promising candidate for the development of value-added health products. However, there is a lack of scientific evidence for its anti-hyperglycemic effects. To address this, we investigated the in vitro and in vivo anti-hyperglycemic and antioxidant effects of salak seed extract. The HPLC chromatogram of salak seed extract shows a prominent peak that corresponds to chlorogenic acid. In vitro studies revealed that salak seeds inhibited α-glucosidase activity and glucose uptake in Caco-2 cells in a concentration-dependent manner, while also exhibiting antioxidant properties. The extract exhibits a non-competitive inhibition on α-glucosidase activity, with an IC₅₀ and K_i of 16.28 ± 7.22 and 24.81 μg/mL, respectively. In vivo studies utilizing streptozotocin-nicotinamide-induced diabetic mice showed that the extract significantly reduced fasting blood glucose (FBG) levels in the oral glucose tolerance test. Continuous administration of the salak seed extract resulted in lower FBG levels by 13.8% as compared with untreated diabetic mice, although this change was not statistically significant. The estimated LD₅₀ value of salak seed extract exceeds 2000 mg/kg, and no toxicity symptoms have been detected. Our research supports that salak seed extract has the potential to serve as a functional food or supplement that may be beneficial in reducing postprandial hyperglycemia among people with type 2 diabetes. This effect was explained by the salak’s inhibitory mechanisms of glucose absorption due to inhibition of both α-glucosidase activity and intestinal glucose uptake, coupled with its antioxidant effects.

The reduction of sugar and the supplementation of bioactive ingredients in gummy jelly help to improve the healthy characteristics of a product that is normally devoid of any nutritional value. Therefore, the objective of this study was to develop a reduced calorie gummy jelly supplemented with Lysiphyllum strychnifolium leaf extract (LS gummy jelly). The gummy jelly was formulated by total substitution of sucrose with a sugar alcohol, xylitol. The antioxidant activities of LS gummy jelly determined by DPPH radical scavenging activity assay was 0.07 ± 0.02 g ascorbic acid equivalent/100 g gummy jelly. The results of ABTS radical scavenging activity and ferric reducing power (FRAP) assay were found to be 0.21 ± 0.02 g TEAC/100 g gummy jelly and 0.98 ± 0.07 mmol FeSO4/100 g gummy jelly, respectively. The percentage inhibition of α-glucosidase activity of LS gummy jelly (at concentration 10 mg/ml) was 46.1 ± 7.9%. The LS gummy jelly was successfully developed with good physical characteristics and negative results for microbiological tests. HPLC quantitative analysis of gallic acid, the major active compound in L. strychnifolium leaf extract, was found to be 0.45 ± 0.04 mg/g of gummy jelly. According to preference ranking test (n=50), the results showed that berry flavor was preferred for LS gummy jelly. Thus, LS gummy jelly could be considered as a promising antioxidant functional food product that could provide health benefits to consumers. Keywords: α-glucosidase, Antioxidant, Gummy jelly, Lysiphyllum strychnifolium