Potential SARS-CoV-2 Mpro steroid inhibitors from Aphanamixis polystachya (Wall.) R. N. Parker

Herein, six previously undescribed steroids (1-6), were isolated from leaves and twigs of Aphanamixis polystachya (Wall.) R. N. Parker (Meliaceae). Their structures were elucidated by comprehensive spectroscopic analysis, including HRESIMS, 1D and 2D NMR, UV, and IR. Antiviral activity of these compounds were evaluated. Compounds 1-6 showed varying degrees of inhibitory activity against the severe acute respiratory syndrome coronavirus 2 main protease (SARS-CoV-2 Mpro) at 200 μM.

Four Unidentified Compounds Isolated from the Stem Barks of Aphanamixis polystachya and Their NO Production Inhibition in LPS Activated RAW 264.7 Cells

Phytochemical study on the methanol extract of the stem barks of Aphanamixis polystachya led to the isolation of four previously undescribed (1-4) and ten known compounds (5-14). Their chemical structures were elucidated to be 11-methoxysawaranospiroride C (1), 6α,9S,10,13-tetrahydroxymegastigmane-3-one (2), 11-hydroxyaphanamixin B (3), (2Z,6E,13E)-2,6,13-triene-11,15-dihydroxyphytanic acid (4), cinnacasside D (5), cinnacasside E (6), vilsonol F (7), (3S,5R,6S,7E,9R)-3,5,6,9-tetrahydroxy-7-en-megastigmane (8), (3S,5R,6R,7E,9R)-3,6,9,10-tetrahydroxy-7-en-megastigmane (9), citroside A (10), threo-1-(3,4,5-trimethoxyphenyl)-1,2,3-propanetriol (11), 3,4,5-trimethoxyphenyl-1-O-β-D-glucopyranoside (12), p-coumaric acid (13), ferulic acid (14) by HR-ESI-MS, ECD, 1D-, and 2D-NMR spectra. Compounds 1, 3, 4, and 9 showed NO production inhibitory activity in LPS activated RAW 264.7 cells with IC50 values of 42.0, 67.9, 20.5, and 78.6 μM, respectively, while the remaining compounds were inactive with IC50 values over 100 μM.

Untargeted Metabolomic Approach to Determine the Regulatory Pathways on Salicylic Acid-Mediated Stress Response in Aphanamixis polystachya Seedlings

Plants thrive under abiotic and biotic stress conditions with the changes in phytohormones like salicylic acid (SA), resulting in the synthesis of secondary metabolites. The present study determines the response of plants in producing secondary metabolites towards different SA concentrations at varying time intervals. Liquid chromatography-mass spectrometry-based metabolomics studies in Aphanamixis polystachya (Wall.) Parker seedlings are grown at 10 mM, 50 mM, and 100 mM SA concentrations, showed the differential expression of metabolites towards the stress. Alkaloids like amaranthin showed a 15-fold increase on the second day, and analog of androvinblastin showed a 20-fold increase on the sixth day in 10 mM SA compared with other groups. Flavanoid cyanidin 3-3 glucosyl was found to be with a 22-fold increment along with terpenoids betavulgaroside (18-fold), asiaticoside (17-fold), mubenin B (20-fold), and deslanoside (22-fold) increment in 50 mM SA on the sixth day. The shock exerted by 100 mM was too harsh, and the lowered metabolite production level was insufficient for the seedlings to survive at this higher SA condition. Arrangement of stressed groups using Pearson correlation studies, principal component analysis, and partial least square analysis placed 10 mM SA and controlled group closer and 50 mM SA and 100 mM SA groups closer to each other. The study observed that SA regulates metabolites that mediate biotic stress responses at low concentrations, and higher concentrations regulate abiotic stress regulating metabolites.

Acyclic diterpene and norsesquiterpene from the seed of Aphanamixis polystachya

Aphanamoxene A-D (1-4), three new acyclic diterpene derivatives and one new acyclic norsesquiterpene were isolated from the seed of Aphanamixis polystachya. Their structures were elucidated on the basis of extensive spectroscopic methods, including 1D and 2D NMR and HRESIMS. And the absolute configuration of 1 was achieved by Mosher method. These acyclic terpenoids (1-4) showed obvious nitric oxide production inhibitory activity on lipopolysaccharide-Induced RAW264.7 macrophages with IC₅₀ values of 17.6 ± 1.4, 9.8 ± 0.7, 16.6 ± 1.2, and 14.2 ± 0.9 μM, respectively.

Two novel nornemoralisin-type diterpenoids from Aphanamixis polystachya (Wall.) R. Parker

Two novel heptanornemoralisin-type diterpenoids nornemoralisins A (1) and B (2), together with two known compounds nemoralisin (3) and nemoralisin A (4), were isolated from the stem bark and leaves of Aphanamixis polystachya (Wall.) R. Parker. Their structures were established through comprehensive analyses of NMR spectroscopic data and high resolution mass spectrometric (HR-ESI-MS) data. The absolute configurations of carbon stereocenters were elucidated by circular dichroism (CD) analyses. The four compounds were tested for their potential cytotoxic effects against ACHN, HeLa, SMMC-7721, and MCF-7 cell lines. Nornemoralisins A (1) and B (2) exhibited significant cytotoxicity on ACHN with an IC₅₀ value of 13.9 ± 0.8 and 10.3 ± 0.4 μM, respectively, and other compounds failed to reveal obvious cytotoxicity on the tested cell lines, compared to positive control vinblastine (IC₅₀, 28.0 ± 0.9 μM).

Diterpenes and Their Derivatives as Potential Anticancer Agents

As therapeutic tools, diterpenes and their derivatives have gained much attention of the medicinal scientists nowadays. It is due to their pledging and important biological activities. This review congregates the anticancer diterpenes. For this, a search was made with selected keywords in PubMed, Science Direct, Web of Science, Scopus, The American Chemical Society and miscellaneous databases from January 2012 to January 2017 for the published articles. A total 28, 789 published articles were seen. Among them, 240 were included in this study. More than 250 important anticancer diterpenes and their derivatives were seen in the databases, acting in the different pathways. Some of them are already under clinical trials, while others are in the nonclinical and/or pre-clinical trials. In conclusion, diterpenes may be one of the lead molecules in the treatment of cancer. Copyright © 2017 John Wiley & Sons, Ltd.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes, labdanes, clerodanes, pimaranes, abietanes, kauranes, gibberellins, cembranes and their cyclization products. The literature from January to December, 2014 is reviewed.