Two new neolignans selaginellol (1) and selaginellol 4′-O-β-d-glucopyranoside (2), together with seven known compounds (3–9), were isolated from the whole plant of Selaginella moellendorffii. The structures of the new isolates were determined through spectroscopic data analysis. Compounds 1–9, as well as compounds 10–18 previously isolated from the species, were measured for the activity against platelet aggregation induced by ADP or collagen. Three neoligans (8, 11, and 12), one flavanone (14), and one alkaloid (16) showed inhibitory activity against ADP- or collagen-induced platelet aggregation as compared with tirofiban. The dihydrobenzofuran neolignans (8, 11, and 12) are more potent than the benzofuran neolignan (13) and other types of neolignans (1–7). Glucosidation of the dihydrobenzofuran neolignans (11 and 12) is helpful for the activity.

Two hydroxychavicol heterodimers comprising phenylpropanoid and monoterpene constituent units, named nudibaccatumins A (1) and B (2), were isolated as an inseparable mixture from the aerial parts of Piper nudibaccatum. Their absolute configurations were confirmed by total synthesis using ortho-alkylation of hydroxychavicol with myrtenyl bromide as the key reaction. The two new compounds (1 and 2) and their synthetic analogues (3–8) were evaluated for XO inhibitory activity.

Three indole alkaloid glycosides, strobilanthosides A–C (1–3), two known indole alkaloid glucosides (4 and 5), and five phenylethanoid glycosides (8–10) were isolated from the aerial parts of Strobilanthes cusia. The structures of the new compounds were elucidated by spectrometric analysis, and the absolute configurations of 1 and 2 were established by ECD spectrocsopy. N′-β-d-Glucopyranosylindirubin (5) showed weak antibacterial activity (MIC 62.5–125 μM) against Staphylococcus aureus.

Twenty-five amide alkaloids (1–25) from Piper boehmeriifolium and 10 synthetic amide alkaloid derivatives (39–48) were evaluated for antiproliferative activity against eight human tumor cell lines, including chemosensitive and multidrug-resistant (MDR) cell lines. The results suggested tumor type-selectivity. 1-[7-(3,4,5-Trimethoxyphenyl)heptanoyl]piperidine (46) exhibited the best inhibitory activity (IC50 = 4.94 μM) against the P-glycoprotein (P-gp)-overexpressing KBvin MDR sub-line, while it and all other tested compounds, except 9, were inactive (IC50 >40 μM) against MDA-MB-231 and SK-BR-3. Structure–activity relationships (SARs) indicated that (i) 3,4,5-trimethoxy phenyl substitution is critical for selectivity against KBvin, (ii) the 4-methoxy group in this pattern is crucial for antiproliferative activity, (iii) double bonds in the side chain are not needed for activity, and (iv), in arylalkenylacyl amide alkaloids, replacement of an isobutylamino group with pyrrolidin-1-yl or piperidin-1-yl significantly improved activity. Further study on Piper amides is warranted, particularly whether side chain length affects the ability to overcome the MDR cancer phenotype.Graphical abstract

•Five phenylphenalenones and two diarylheptanoids were isolated from Musa itinerans.•A putative biosynthetic pathway to the phenylphenalenone-related heterodimer is proposed.•Two of the phenylphenalenones exhibited weak cytotoxic effects against a human lung adenocarcinoma cell line.Two diarylheptanoids, musaitinerins A and B, one heterodimeric phenylphenalenone musaitinerone and four known phenylphenalenones, identified as 4-hydroxy-2-methoxy-9-phenyl-1H-phenalen-1-one, musanolone E, hydroxyanigorufone and irenolone were isolated from the fruits of Musa itinerans Cheesm. Their structures were elucidated using spectroscopic analyses. The antimicrobial activity of these compounds was evaluated against Escherichia coli, Staphylococcus aureus and Candida albicans; the cytotoxic activity of these compounds was also evaluated against human erythromyeloblastoid leukemia (K562) and human alveolar carcinoma epithelial (A549) cell lines, respectively. Musaitinerone and musanolone E exhibited weak effects against the A549 cell line, as compared with adriamycin. However, these two compounds did not exhibit any growth inhibition against K562 cells, S. aureus, E. coli or C. albicans. The other compounds were inactive against all of the tested cell lines and microorganisms, even at concentrations as high as 50 μM.Two diarylheptanoids, one dimeric phenylphenalenone and four known phenylphenalenones were isolated from Musa itinerans. Two of the phenylphenalenones exhibited weak effects against a human lung adenocarcinoma cell line.

A new complex natural product with a C39 skeleton, named nudibaccatumone, and the known sesquiterpenes (+)-spathulenol, (−)-4β,10α-aromadendranediol, and ent-T-muurolol, as well as the phenylpropanoid hydroxychavicol, were isolated from the aerial parts of Piper nudibaccatum. The structure and absolute configuration of nudibaccatumone were elucidated using spectroscopic methods and ECD calculations. A 1,8-Michael addition reaction and an intermolecular, inverse electron demand Diels–Alder reaction are proposed as the key steps in the biosynthesis of nudibaccatumone.

•Gmelina arborea flower is a medicinal-edible plants in Xishuangbanna, China.•The major chemical components including 5 new compounds of G. arborea flower were isolated and identified.•The in vitro hepatoprotective activity of selected chemical constituents were tested.Nine acylated iridoid glycosides (1–9), five acylated rhamnopyranoses (10–14) and verbascoside (15) were isolated from Gmelina arborea flowers, including 5 new compounds (1, 2, and 10–12). The cytoprotective activity of 11 selected compounds (1–8, 10, 11, and 15) against CCl4-induced cytotoxicity on liver was determined. Compounds 1, 2, 4, 7, 8 and 15 displayed hepatoprotective activity. 6-O-α-l-(2″, 3″-di-O-trans-p-hydroxycinnamoyl)rhamnopyranosylcatalpol (2) exhibited the most potent cytoprotective effect with an EC50 value of 42.5 μM (SI = 19.3) compared with biphenyldimethylesterate (DDB, EC50 = 277.3 μM, SI = 9.8) and bicylo-ethanol (EC50 = 279.2 μM, SI = 12.2). Among the acylated iridoid glycosides, the compounds (2 and 8) containing phenolic hydroxy groups were more active than were those lacking them.

Palhinine A, a novel C16N-type Lycopodium alkaloid with a unique 5/6/6/9 tetracyclic ring system, was isolated from the whole plant of Palhinhaea cernua L. (Lycopodiaceae). Its structure was elucidated by spectroscopic methods, and the absolute configuration was determined by single-crystal X-ray diffraction analysis using the Flack parameter. Palhinine A is reported as the first example of Lycopodium alkaloids of which C-16 is fused to a new ring through a C-16−C-4 lingkage.

The ethnomedical uses of Piper (胡椒 Hú Jiāo) plants as anticancer agents, in vitro cytotoxic activity of both extracts and compounds from Piper plants, and in vivo antitumor activity and mechanism of action of selected compounds are reviewed in the present paper. The genus Piper (Piperaceae) contains approximately 2000 species, of which 10 species have been used in traditional medicines to treat cancer or cancer-like symptoms. Studies have shown that 35 extracts from 24 Piper species and 32 compounds from Piper plants possess cytotoxic activity. Amide alkaloids account for 53% of the major active principles. Among them, piplartine (piperlongumine) shows the most promise, being toxic to dozens of cancer cell lines and having excellent in vivo activity. It is worthwhile to conduct further anticancer studies both in vitro and in vivo on Piper plants and their active principles.