Two new compounds, dihydrodengibsinin (1) and dendrogibsol (2), were isolated from the whole plant of Dendrobium gibsonii, together with seven known compounds (3–9). The structures of the new compounds were elucidated by their spectroscopic data. All these isolates were evaluated for their α-glucosidase inhibitory activities. Dendrogibsol (2) and lusianthridin (7) showed strong α-glucosidase inhibitory activity when compared with acarbose. An enzyme kinetic study revealed that dendrogibsol (2) is a noncompetitive inhibitor of α-glucosidase.
Chemical investigation of Dendrobium delacourii revealed 11 phenolic compounds, and the structures of these compounds were determined by analysis of their NMR and HR-ESI-MS data. All compounds were investigated for their α-glucosidase inhibitory activity and anti-adipogenic properties. Phoyunnanin E (10) and phoyunnanin C (11) showed the most potent α-glucosidase inhibition by comparing with acarbose, which was used as a positive control. Kinetic study revealed the non-competitive inhibitors against the enzyme. For anti-adipogenic activity, densifloral B (3) showed the strongest inhibition when compared with oxyresveratrol (positive control). In addition, densifloral B might be responsible for the inhibition of adipocyte differentiation via downregulating the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT enhancer-binding protein alpha (C/EBPα), which are major transcription factors in adipogenesis.
A phytochemical investigation on the whole plants of Aerides multiflora revealed the presence of three new biphenanthrene derivatives named aerimultins A–C (1–3) and a new natural phenylpropanoid ester dihydrosinapyl dihydroferulate (4), together with six known compounds (5–10). The structures of the new compounds were elucidated by analysis of their spectroscopic data. All of the isolates were evaluated for their a-glucosidase inhibitory activity. Aerimultin C (3) showed the most potent activity. The other compounds, except for compound 4, also exhibited stronger activity than the positive control acarbose. Compound 3 showed non-competitive inhibition of the enzyme as determined from a Lineweaver–Burk plot. This study is the first phytochemical and biological investigation of A. multiflora.
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