Screening of Various Parts of Phaleria macrocarpa Plant for α-Glucosidase Inhibitory Activity

Phaleria macrocarpa is an herbal plant used in Malaysia to enhance vitality. The aim of this study was to screen the α-glucosidase inhibitory activity of different parts (fruit flesh, leaves and stem) of P. macrocarpa. Methanol (polar) and n-hexane (nonpolar) extracts, obtained by room temperature solvent extraction, were evaluated for in vitro α-glucosidase activity inhibition. The compounds were identified by using gas chromatography-mass spectrometry (GC-MS) according to their similarity index of >70%, which might be responsible for α-glucosidase inhibitory activity. The methanol extract of the fruit flesh had the highest yield (25.6 ± 0.5%), whereas the n-hexane extract of the stem is more effective against α-glucosidase activity (IC₅₀ 0.8 ± 0.1 μg/mL). The fruit flesh (IC₅₀1.3 ± 0.2 μg/mL) and leaves (IC₅₀1.6 ± 0.6 μg/mL) had also well effectively. The identified metabolites are predominantly phenolics, carbohydrates, triterpenes and organic acids, such as D-fructose, squalene, α-linolenic acid and α-D-glucopyranoside. In-depth chemical profiling using GC-MS was performed for the first time for this plant to assess the likely compounds present in the extract that could be associated with anti-hyperglycemic activity. Of the three parts tested, every part indicates the potential α-glucosidase inhibitory activity and hexane extract of stem showed more inhibitory activity among all extracts. Thus, P. macrocarpa can attenuate hyperglycemia by potently inhibiting carbohydrate hydrolyzing enzymes, making it a viable plant as a source of natural compounds for the management of type 2 diabetes mellitus.

Practical Application

P. macrocarpa (Scheff.) Boerl. belongs to the Thymelaeaceae family, which is known as “Mahkota Dewa” is one of the well-known traditional herbs in South Asian countries. Every part of this plant has been reported to be used as a traditional medicine for diabetic treatment for many years. In the present study, the ability of this plant to inhibit carbohydrate hydrolyzing enzymes (α-glucosidase) was explored. All extracts tested exhibited the content to inhibit yeast α-glucosidase enzymes in vitro, and these beneficial effects appear to be due to some bioactive compounds in P. macrocarpa. Our preliminary investigation gives a principle for further animal and clinical studies of a possible use of P. macrocarpa for the management of diabetes mellitus.