Conservation genomic study of Hopea hainanensis (Dipterocarpaceae), an endangered tree with extremely small populations on Hainan Island, China.

Introduction: Hopea hainanensis Merrill & Chun is considered a keystone and indicator species in the tropical lowland rainforests of Hainan Island. Owing to its high-quality timber, H. hainanensis has been heavily exploited, leading to its classification as a first-class national protected plant in China and a plant species with extremely small populations (PSESPs). Methods: This study analyzed genome-wide single nucleotide polymorphisms obtained through restriction site-associated DNA sequencing from 78 adult trees across 10 H. hainanensis populations on Hainan Island. Results and discussion: The nucleotide diversity of the sampled populations ranged from 0.00096 to 0.00138, which is lower than that observed in several other PSESPs and endangered tree species. Bayesian unsupervised clustering, principal component analysis, and neighbor-joining tree reconstruction identified three to five genetic clusters in H. hainanensis, most of which were geographically widespread and shared by multiple populations. Demographic history analysis based on pooled samples indicated that the decline in the H. hainanensis population began approximately 20,000 years ago, starting from an ancestral population size of approximately 10,000 individuals. The reduction in population size accelerated approximately 4,000 years ago and has continued to the present, resulting in a severely reduced population on Hainan Island. Intensified genetic drift in small and isolated H. hainanensis populations may contribute to moderate differentiation between some of them, as revealed by pairwise F st. In conclusion, our conservation genomic study confirms a severe population decline and an extremely low level of nucleotide variation in H. hainanensis on Hainan Island. These findings provide critical insights for the sustainable management and genetic restoration of H. hainanensis on Hainan Island.

2-(2-Phenylethyl)chromone derivatives: Promising α-glucosidase inhibitors in agarwood from Aquilaria filaria.

Twelve undescribed 2-(2-phenylethyl)chromone derivatives, including one pair of enantiomers, together with eleven known ones, were isolated from the EtOAc extract of agarwood originating from Aquilaria filaria. All structures were elucidated by spectroscopic (NMR, UV, IR, MS) methods and compared with reported data in literatures. Twenty-one compounds were assessed for α-glucosidase inhibitory activity, which showed inhibition of α-glucosidase with IC50 values ranging between 7.8 ± 0.3 to 137.7 ± 3.0 µM (Acarbose, 743.4 ± 3.3 µM; Genistein, 8.3 ± 0.1 µM). Our results expanded the structural diversity of 2-(2-phenylethyl)chromones from agarwood, and revealed the potential of 2-(2-phenylethyl)chromones as α-glucosidase inhibitors.

Four new guaiane sesquiterpenoids from agarwood of Aquilaria filaria.

Six 8,12-epoxyguaiane sesquiterpenes (1-6), together with two known 2-(2-phenylethyl)chromone derivatives (7-8) were isolated from agarwood originating from Aquilaria filaria. Their structures were established by spectroscopic methods including IR, HRESIMS, 1D, and 2D NMR, and comparison with the published data. The absolute configuration of compound 1 was unambiguously determined by quantum chemical calculation of the electronic circular dichroism (ECD) spectrum. All compounds were tested for their α-glucosidase inhibitory activity and cytotoxicity. Compound 5 showed significant α-glucosidase inhibitory activity with IC50 value of 253.2 ±â€¯9.7 µM (Acarbose, 743. 4 ±â€¯3.3 µM). Compounds 2-4 displayed weak cytotoxicity against K562 tumor cell lines.