Ebola virus disease (EVD), a disease caused by infection with Ebola virus (EBOV), is characterized by hemorrhagic fever and a high case fatality rate. With limited options for the treatment of EVD, anti-Ebola viral therapeutics need to be urgently developed. In this study, over 500 extracts of medicinal plants collected in the Lingnan region were tested against infection with Ebola-virus-pseudotyped particles (EBOVpp), leading to the discovery of Maesa perlarius as an anti-EBOV plant lead. The methanol extract (MPBE) of the stems of this plant showed an inhibitory effect against EBOVpp, with an IC₅₀ value of 0.52 µg/mL, which was confirmed by testing the extract against infectious EBOV in a biosafety level 4 laboratory. The bioassay-guided fractionation of MPBE resulted in three proanthocyanidins (procyanidin B2 (1), procyanidin C1 (2), and epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin (3)), along with two flavan-3-ols ((+)-catechin (4) and (−)-epicatechin (5)). The IC₅₀ values of the compounds against pseudovirion-bearing EBOV-GP ranged from 0.83 to 36.0 µM, with 1 as the most potent inhibitor. The anti-EBOV activities of five synthetic derivatives together with six commercially available analogues, including EGCG ((−)-epigallocatechin-3-O-gallate (8)), were further investigated. Molecular docking analysis and binding affinity measurement suggested the EBOV glycoprotein could be a potential molecular target for 1 and its related compounds.

Cancer is a leading cause of mortality in the world and metastasis is to blame. Invasion is the initial step of metastasis. Therapies targeting epithelial–mesenchymal transition (EMT), cancer stem cells (CSCs) and signal transducer and activator of transcription 3 (STAT3) signaling pathways can reduce stemness of cancer cells and thus inhibit cancer invasion. A large number of anti-cancer naphthoquinones (NQs) can target cancer invasion by acting on EMT, CSCs and STAT3 signaling. Furano-naphthoquinones (FNQs) belong to a class of NQ derivatives commonly characterized by a naphthoquinone fused with a furano ring. A study indicated that the corporation of the furano ring improved the anticancer potency as compared to the other classes of NQs. BBI608, a natural FNQ, which can be found in the woods or barks of several Tabebuia species, has entered phases I and II clinical trials. It has been regarded as a potential candidate for new-generation lead compound acting directly on CSCs to overcome the chemotherapy resistance. Apart from the natural plant sources, there are a number of synthetic FNQ derivatives that are effective in reducing stemness of cancer cells and thus are anti-invasive. In this review, the anti-invasion mechanisms of NQs and the more powerful FNQs, together with their natural origins, synthetic derivatives as well as their synthetic routes are discussed.

Three isopimarane diterpenes [fladins B (1), C (2), and D (3)] were isolated from the twigs and leaves of Chinese folk medicine, Isodon flavidus. The chemical structures were determined by the analysis of the comprehensive spectroscopic data, and the absolute configuration was confirmed by X-ray crystallographic analysis. The structures of 1–3 were formed from isopimaranes through the rearrangement of ring A by the bond break at C-3 and C-4 to form a new δ-lactone ring system between C-3 and C-9. This structure type represents the first discovery of a natural isopimarane diterpene with an unusual lactone moiety at C-9 and C-10. In the crystal of 1, molecules are linked to each other by intermolecular O-H···O bonds, forming chains along the b axis. Compounds 1–3 were evaluated for their bioactivities against different diseases. None of these compounds displayed cytotoxic activities against HCT116 and A549 cancer cell lines, antifungal activities against Trichophyton rubrum and T. mentagrophytes, or antiviral activities against HIV entry at 20 µg/mL (62.9–66.7) µM. Compounds 1 and 3 did not show antiviral activities against Ebola entry at 20 µg/mL either; only 2 was found to show an 81% inhibitory effect against Ebola entry activity at 20 µg/mL (66.7 µM). The bioactivity evidence suggested that this type of compound could be a valuable antiviral lead for further structure modification to improve the antiviral potential.

Two new tigliane diterpenes, named eupneonoids A (1) and B (2), together with four known analogues (3–6) were isolated from the whole plant of Euphorbia neorubella Bruyns. Their structures were deduced based on the detailed spectroscopic analysis. All the isolates displayed cytotoxic effects against A549 human tumor cell lines with IC₅₀ values ranging from 1.318 to 7.042 μM. Graphical Abstract