Structural Characterization and Anti-infective Activity of 9,10-Seco-29-norcycloartane Glycosides Isolated from the Flowers of the Peruvian Medicinal Plant Cordia lutea

Cytotoxic Activities of 9,10-seco-Cycloartane-Type Triterpenoids from the Chinese Liverwort Lepidozia reptans

Ten new triterpenoids, including nine 9,10-seco-cycloartanes (1-9) and one 9,19-cyclolanostane (10), as well as one sesquiterpenoid (11) and four known compounds (12-15), were extracted and purified from the whole plant of the Chinese liverwort Lepidozia reptans. Multiple techniques (NMR, HRESIMS, IR, and X-ray crystallographic analysis) were applied to determine the structures of the isolated compounds. Bioassay determinations showed that compound 7, which contains an α,β-unsaturated carbonyl moiety in its structure, inhibited the growth of a panel of cancer cell lines with IC₅₀ values ranging from 4.2 ± 0.2 to 5.7 ± 0.5 μM. Further investigation revealed that compound 7 induces PC-3 cell death via mitochondrial-related apoptosis.

Reproducibility challenges in the search for antibacterial compounds from nature

Background

Reproducibility of reported antibacterial activities of plant extracts has long remained questionable. Although plant-related factors should be well considered in serious pharmacognostic research, they are often not addressed in many research papers. Here we highlight the challenges in reproducing antibacterial activities of plant extracts.

Methods

Plants with reported antibacterial activities of interest were obtained from a literature review. Antibacterial activities against Escherichia coli and Klebsiella pneumoniae were tested using extracts’ solutions in 10% DMSO and acetone. Compositions of working solutions from both solvents were established using LC-MS analysis. Moreover, the availability of details likely to affect reproducibility was evaluated in articles which reported antibacterial activities of studied plants.

Results

Inhibition of bacterial growth at MIC of 256–1024 μg/mL was observed in only 15.4% of identical plant species. These values were 4–16-fold higher than those reported earlier. Further, 18.2% of related plant species had MICs of 128–256 μg/mL. Besides, 29.2% and 95.8% of the extracts were soluble to sparingly soluble in 10% DMSO and acetone, respectively. Extracts’ solutions in both solvents showed similar qualitative compositions, with differing quantities of corresponding phytochemicals. Details regarding seasons and growth state at collection were missing in 65% and 95% of evaluated articles, respectively. Likewise, solvents used to dissolve the extracts were lacking in 30% of the articles, whereas 40% of them used unidentified bacterial isolates.

Conclusion

Reproducibility of previously reported activities from plants’ extracts is a multi-factorial aspect. Thus, collective approaches are necessary in addressing the highlighted challenges.

Bioactive Isocedrenes from Perezia multiflora

Four isocedrenes (1:  - 4: ), including one new compound (2: ), were isolated from an ethanolic extract of the aerial parts of Perezia multiflora by bioactivity-guided fractionation. For compounds 1: and 3: , a revised stereochemical assignment is proposed based on molecular modeling studies using DFT-NMR calculations. Antiparasitic activity of the four compounds was evaluated using an in vitro culture of Plasmodium falciparum and axenic amastigotes of Leishmania infantum. IC₅₀ values ranged from 0.81 to 16.1 µM (P. falciparum) and 0.16 to 2.03 µM (L. infantum). Toxicity was evaluated against J774A.1 mouse macrophages or human macrophages generated from THP-1 monocytic cells (IC₅₀ values ranging from 0.16 to 2.64 µM). Compound 4: exhibited weak selectivity against P. falciparum with a selectivity index (SI = CC₅₀/IC₅₀) of 3. No selectivity was observed for compounds 1:  - 3: against both parasites.