Antioxidant, Anti-Inflammatory and Anti-Diabetic Activities of Tectona grandis Methanolic Extracts, Fractions, and Isolated Compounds

Tectona grandisis a traditional Dai medicine plant belonging to the Lamiaceae family, which can be used to treat malaria, inflammation, diabetes, liver disease, bronchitis, tumors, cholelithiasis, jaundice, skin disease and as an anti-helminthic. To find more novel therapeutic agents contained in this medicinal plant, the antioxidant, anti-inflammatory and anti-diabetic activities ofT. grandismethanolic extract, fractions and compounds were evaluated. In this study, 26 compounds were isolated from the leaves and branches ofT. grandis. Their structures were identified based on extensive spectral experiments, including NMR, ESI-MS and comparison with published spectral data. Among them, compounds1–2,4–6,9–14and16–22were reported for the first time for this plant. The antioxidant activity screening results showed that compounds5,15and23had potent antioxidant capacities, with SC50values from 0.32 to 9.92 µmol/L, 0.92 to 1.10 mmol Trolox/L and 1.02 to 1.22 mmol Trolox/L for DPPH, ABTS and FRAP, respectively. In addition, their anti-inflammatory effects were investigated by releasing TNF-α, IL-1βand IL-6 through the use of mouse monocytic macrophages (RAW 264.7). Compounds1,13,18and23had the effects of reducing the expression of inflammatory factors. Compounds13and18were reported for the first time for their anti-inflammatory activities. Furthermore, the methanolic extract (ME), petroleum ether extract (PEE) and EtOAc extract (EAE) ofT. grandisshowed significant glucose uptake activities; compounds21and23significantly promoted glucose uptake of 3T3-L1 adipocytes at 40 µM. Meanwhile, compounds4,5and7showed significant inhibitory activities against α-glucosidase, with IC50values of 14.16 ± 0.34 µmol/L, 19.29 ± 0.26 µmol/L and 3.04 ± 0.08 µmol/L, respectively. Compounds4and5were reported for the first time for theirα-glucosidase inhibitory activities. Our investigation explored the possible therapeutic material basis ofT. grandisto prevent oxidative stress and related diseases, especially inflammation and diabetes.Keywords:Tectona grandis;chemical composition;antioxidant activity;anti-inflammatory activity;α-glucosidase;glucose uptake