Evaluation of DPPH Free Radical Scavenging, α-Glucosidase Inhibitory, and Antimicrobial Activities of Aquilaria malaccensis Leaf Extracts

Herbs and medicinal plants are major ingredients in traditional or folk medicine for many countries of the world, including Malaysia. This study evaluated the potential of the leaf extract in different solvent polarities and drying methods of Aquilaria malaccensis, in scavenging free radicals and inhibiting the enzyme α-glucosidase as well as antimicrobial activities. Both methanol and ethanol extracts in oven dry method were efficient solvents to extract the antioxidant constituents of A. malaccensis. To analyze α-glucosidase inhibitory activity, the methanol extracts of A. malaccensis in air dry method exhibited the highest activity with an IC50 value of 196.31 μg/mL. In addition, for the antimicrobial activity, each extract was tested by a serial two-fold dilution method against selected Gram-positive bacteria and Gram-negative bacteria, and this suggested that hexane in oven dry method possessed the maximum antimicrobial activity against the gram-positive bacteria tested. It is suggested that the antioxidant and antidiabetic properties were exhibited most in a polar solvent (MEOH) whether in air dry or oven dry method with no significant difference. In contrary with antimicrobial which was efficient in a non-polar solvent (HEX) in oven dry method. These results indicate that A. malaccensis is a promising source as herbal medicine

Evaluation of the DPPH Radical Scavenging Activity, Total Phenolic Content and Total Flavonoid Content of Different Solvent Extracts of Catunaregam tomentosa (Blume ex DC) Tirveng Leaves

Catunaregam tomentosa (Blume ex DC) Tirveng is commonly known as Khet in Thailand and Bisa Ular or Badang in Malaysia. The tree is widely distributed in the north-east region of Thailand while in Malaysia the tree usually grows in the open waterfront area at Terengganu. This plant belongs to the Rubiaceae family, and the genus catunaregam has interesting pharmacological activities such as anti-inflammatory, antispasmodic, antidysenteric, antifertility and immunomodulatory. In this study, the leaves were extracted using dichloromethane, ethyl acetate and ethanol. Total phenolic was determined by Folin-Ciocalteau method while total flavonoid was determined by the aluminium chloride calorimetric method. Meanwhile, its antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The ethanolic extract was found to have the highest percentages of phenolic and flavonoid content. Interestingly, ethanolic extract also demonstrated strong DPPH scavenging activity with IC50 at 20.07 ± 0.51µg/mL

Effects of drying methods and solvents on phenolic and flavonoids content, DPPH radical scavenging and alpha-glucosidase activities of Aquilaria leaves extract

Aquilaria is a multipurpose plant with high commercial and medicinal values. The present study aimed to evaluate the effects of drying methods and extraction solvents on the phenolic and flavonoids content in A. malaccensis (AMA), A. subintegra (ASU), and A. sinensis (ASI). Leaf samples were either Air-Dried (AD) or Oven-Dried (OD) and extracted using 100% Ethanol (EE100), 70% ethanol (EE70), aqueous (AE), and hexane (HE). There was a significant difference (p<0.05) between the drying methods and the extracting solvents. The OD in AMA leaf samples gave the highest values of total phenolic compounds (TPC) (52.98 – 85.15 mg GAE/gm) and total flavonoid compounds (TFC) (2180.97 – 3733.45 QUE ppm). The highest DPPH radical scavenging was observed in OD-EE70-AMA with the IC50 value of 33.60 µg/mL. Meanwhile, OD-EE100-AMA gave the lowest IC50 value (0.13 µg/mL) in the α-glucosidase assay, followed by OD-EE70-AMA with IC50 value 0.69 µg/mL with no significant differences among them. OD-EE70-AMA was found to have a higher content of TPC and TFC with the most potent DPPH scavenging and α-glucosidase inhibition activities. A strong positive correlation was reported between bioassays and TPC or TFC, hence indicating that AMA leaf used in this study might have the potential as a natural antioxidant and an antidiabetic agent

Determination of Total Phenolics, Flavonoids, and Antioxidant Activity and GC-MS Analysis of Malaysian Stingless Bee Propolis Water Extracts

Propolis contains polyphenolic compounds such as flavonoids and phenols that are able to demonstrate a broad spectrum of biological activities including antioxidant, antibacterial, and many more. This study was carried out to determine the total phenolics, flavonoids, and antioxidant activity of water-extracted propolis samples from three different Indo-Malayan stingless bee species, namely, Tetrigona apicalis, Tetrigona binghami, and Homotrigona fimbriata. Total phenolic and flavonoid contents were evaluated using Folin–Ciocalteu colorimetric and aluminium chloride methods, respectively, while the antioxidant activity was analysed using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay. Results indicated that H. fimbriata extracts exhibit the highest TPC, TFC, and antiradical activity among all samples tested. Interestingly, the data also showed that the higher the concentration of the extract used, the higher the antioxidant activity exhibited by the samples. Statistically, there were no significant differences recorded between the different bee species’ propolis studied. In conclusion, the propolis extracts showed stronger antioxidant potential with higher TPC and TFC values. This study also noted the presence of bioactive compounds from local stingless bee propolis that could potentially be utilised for their medicinal and health benefits