chiro-Inositol Derivatives from Chisocheton paniculatus Showing Inhibition of Nitric Oxide Production

Homalolides C-D, two new sesquiterpenoids from the rhizomes of Homalomena pendula

Two new sesquiterpenoids, homalolides C - D (1‒2), were co-isolated from the rhizomes of Homalomena pendula (Blume) Bakh.f collected in Vietnam with five known ones, aromadendrane-4α,10α-diol (3), bullatantriol (4), 1β,4β,6α-trihydroxy-eudesmane (5), 1β,4β,6β-trihydroxyeudesmane (6), and 1β,4β,7α-trihydroxy-eudesmane (7). The structures and relative configuration of new compounds were elucidated by 1 D-/2D-NMR, IR, UV and HRESIMS analyses, and by comparisons to the reported data in the literature. Homalolide C presented an unprecedented skeleton with the 4/8 bicyclic system. All isolates did not exhibit appreciable inhibitory effects on LPS-induced NO production in the RAW 264.7 macrophage cell line and on the growth of human lung cancer cell line (SK-LU-1).

Conarubins A-D: Four Monoterpene-Chalcone Conjugates from Conamomum rubidum and Their Anti-inflammatory and Cytotoxic Activities

Four novel compounds, conarubins A-D (1-4), were isolated from the whole plants of Conamomum rubidum collected in Vietnam. Their structures were elucidated by extensive spectroscopic analyses and by quantum chemical calculations of NMR and ECD. Compounds 1 and 2 were the first examples of monoterpene-monoterpene-chalcone conjugates in nature, whereas compound 4 was an unprecedented monoterpene-substituted chalcone containing a 3,4,5-trioxygenated cyclohexa-2,5-diene-1-one ring. The anti-inflammatory and cytotoxic activities of all isolates were investigated.

d-chiro-Inositol Derivatives with Multidrug Resistance Reversal Activities from the Fruits of Chisocheton siamensis

Chisosiamols A-K (1-11), 11 new d-chiro-inositol derivatives, along with a known analogue (12) were isolated from the fruits of Chisocheton siamensis. Their planar structures and relative configurations were elucidated by the comprehensive application of spectroscopic methods, especially from the characteristic coupling constants, and ¹H-¹H COSY spectra. The absolute configurations of the d-chiro-inositol core were determined using the ECD exciton chirality and X-ray diffraction crystallographic analytical methods. This is the first crystallographic data reported for the d-chiro-inositol derivatives. A structural elucidation strategy mainly combining ¹H-¹H COSY correlations and ECD exciton chirality for determining the structure of d-chiro-inositol derivatives was developed, which also led to the revisions of previously reported structures. Bioactivity evaluation indicated that chisosiamols A, B, and J can reverse multidrug resistance in MCF-7/DOX cells in the IC₅₀ range of 3.4-6.5 μM (RF: 3.6-7.0).

Inositol Derivatives with Anti-Inflammatory Activity from Leaves of Solanum capsicoides Allioni

Eight new inositol derivatives, solsurinositols A-H (1-8), were isolated from the 70% EtOH extract of the leaves of Solanum capsicoides Allioni. Careful isolation by silica gel column chromatography followed by preparative high-performance liquid chromatography (HPLC) allowed us to obtain analytically pure compounds 1-8. They shared the same relative stereochemistry on the ring but have different acyl groups attached to various hydroxyl groups. This was the first time that inositol derivatives have been isolated from this plant. The chemical structures of compounds 1-8 were characterized by extensive 1D nuclear magnetic resonance (NMR) and 2D NMR and mass analyses. Meanwhile, the in vitro anti-inflammatory activity of all compounds was determined using lipopolysaccharide (LPS)-induced BV2 microglia, and among the isolates, compounds 5 (IC₅₀ = 11.21 ± 0.14 µM) and 7 (IC₅₀ = 14.5 ± 1.22 µM) were shown to have potential anti-inflammatory activity.

Sesquiterpenoids from the rhizomes of Homalomena pendula and their anti-inflammatory activities

Sixteen sesquiterpenoids including two new ones, homalolides A - B (1‒2), were firstly isolated from the methanolic extract of the rhizomes of Homalomena pendula collected in Vietnam. The structures and relative stereochemistry of new compounds were elucidated by 1D-/2D-NMR, IR, UV and HRESIMS analyses. The GCMS experiment demonstrated that homalolide A (1) is an artifact due to the methylation during methanolic extraction process. All isolates (1‒16) were tested for their inhibitory activities against lipopolysaccharide-induced nitric oxide production in the RAW 264.7 macrophage cell line. Compounds 1, 3, 6‒8, 10‒12 displayed moderate inhibitory effect on NO production with IC₅₀ values ranging from 35.41 to 64.06 μM.

Glycoside constituents from Miliusa sinensis leaves and their anti-inflammatory and acetylcholine protective effects

Repeated column chromatography resulted in the isolation of two new glycosides, miliusides A-B (1 and 7), along with six known metabolites (2-6, and 8) from the leaves of Miliusa sinensis Finet and Gagnep. The structures of the purified phytochemicals were elucidated by interpreting their spectroscopic data (NMR, HRMS), as well as comparison with the previous literature. The biological evaluation of acetylcholinesterase (AChE) inhibitory effects and anti-inflammatory activity by measuring nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 mouse macrophage cells, were also conducted. Among them, compounds 5 and 7 exhibited significant AChE inhibitory activities (IC₅₀ = 53.36 ± 4.20 and 88.50 ± 8.79 µM, respectively), compared with the positive control (Galanthamine, IC₅₀ = 1.65 ± 0.15 µM). Only the MeOH extract showed suppression effects on NO production in LPS-induced RAW264.7 cells (IC₅₀ = 38.18 ± 3.25 μg/mL) comparable to that of the positive control, l-NMMA (IC₅₀ = 2.21 ± 0.56 μg/mL).

Survey of natural products reported by Asian research groups in 2020

The new natural products reported in 2020 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2020 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.