Inhibition of nitric oxide production by clerodane diterpenoids from leaves and stems of Croton poomae Esser

Spermacosides a and B, two new triterpenoid saponins from Spermacoce ocymoides burm.f

Two new triterpenoid saponins, named spermacosides A-B (1 - 2), together with two known oleanane-type triterpenoid saponins, 3-O-β-D-xylopyranosyl-(1→3)-β-D-glucopyranosylbayogenin (3) and 3-O-β-D-glucopyranosylbayogenin (4), were isolated from the ethyl acetate extract of Spermacoce ocymoides Burm.f. in a phytochemical investigation. Their chemical structures were elucidated by spectroscopic data analysis (1D and 2D NMR, and HR-ESI-MS), as well as comparison with reported data. All these compounds were evaluated for inhibiting nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 cells. Among them, 1 showed a slight effect with an IC50 value of 108.65 ± 7.91 µM, and compounds 2-4 were inactive.

Anti-Inflammatory and Cytotoxic Activities of Clerodane-Type Diterpenes

The secondary metabolites of clerodane diterpenoids have been found in several plant species from various families and in other organisms. In this review, we included articles on clerodanes and neo-clerodanes with cytotoxic or anti-inflammatory activity from 2015 to February 2023. A search was conducted in the following databases: PubMed, Google Scholar and Science Direct, using the keywords clerodanes or neo-clerodanes with cytotoxicity or anti-inflammatory activity. In this work, we present studies on these diterpenes with anti-inflammatory effects from 18 species belonging to 7 families and those with cytotoxic activity from 25 species belonging to 9 families. These plants are mostly from the Lamiaceae, Salicaceae, Menispermaceae and Euphorbiaceae families. In summary, clerodane diterpenes have activity against different cell cancer lines. Specific antiproliferative mechanisms related to the wide range of clerodanes known today have been described, since many of these compounds have been identified, some of which we barely know their properties. It is very possible that there are even more compounds than those described today, in such a way that makes it an open field to discover. Furthermore, some diterpenes presented in this review have already-known therapeutic targets, and therefore, their potential adverse effects can be predicted in some way.

Cytotoxic ent-abietane diterpenoids from the leaves of Croton lachnocarpus Benth

A phytochemical investigation on the 90% ethanol extract of the leaves of Croton lachnocarpus Benth. led to three new ent-abietane diterpenoids, 7β,15-dihydroxy-ent-abieta-8,11,13-trien-3-one (1), 2β,15-dihydroxy-ent-abieta-8,11,13-triene (2), and 7β,13α,15-trihydroxy-ent-abieta-8(14)-en-3-one (3). Structural elucidation of all the compounds were performed by spectral methods such as 1 D and 2 D (¹H-¹H COSY, HMQC, NOESY and HMBC) NMR spectroscopy, in addition to electronic circular dichroism (ECD) spectra. The isolated compounds were tested in vitro for cytotoxic activity against 6 tumor cell lines. As a result, compound 3 exhibited some cytotoxicities against all the tested tumor cell lines with IC₅₀ value less than 30 μM.

Antimicrobial ent-abietane diterpenoids from the leaves of Croton cascarilloide

Three new ent-abietane diterpenoids, 6β-hydroxy-ent-abieta-7,13-dien-3-one (1), 2β,13α,15-trihydroxy-ent-abieta-8(14)-en-3-one (2), and 2β,9α,13β,15-tetrahydroxy-ent-abieta-7-en-3-one (3), were isolated from 90% ethanol extract of the leaves of Croton cascarilloide. Their structures were determined by spectral methods such as 1D and 2D (¹H-¹H COSY, HMQC, NOESY, and HMBC) NMR spectroscopy, in addition to electronic circular dichroism (ECD) spectra. The isolated diterpenoids were tested in vitro for antimicrobial activity against 6 pathogenic microorganisms. As a result, compounds 1-3 exhibited antimicrobial activity against the tested Gram positive bacteria with minimum inhibitory concentration values less than 50 μg/ml.

Phytochemical Analysis and Investigation of the Antimicrobial and Cytotoxic Activities of Croton dichogamus Pax Crude Root Extracts

Background

Increasing antimicrobial resistance has led to an arduous search for new potent drugs from nature. In this search, plants have proved to be rich reservoirs of efficacious medicinal components that manage ailments. The current study is designed to investigate the phytochemical composition, antimicrobial activity, and the cytotoxicity of the crude root extracts of Croton dichogamus, a shrub that is commonly used in the eastern Africa for the management of infectious diseases.

Methods

The roots of Croton dichogamus were obtained, dried, ground, and extracted using three solvents (acetone, distilled water, and 50% ethanol). The antimicrobial activity was tested using agar well diffusion and microbroth dilution techniques against five human pathogens. The brine shrimp lethality assay was used to assess the toxic effect.

Results

The phytochemical screening indicated the presence of terpenoids, flavonoids, tannins, phenols, polyuronides, saponins, and anthracenes. The brine shrimp lethality assay indicated that all the extracts were highly cytotoxic with LC₅₀ values below 100 μg/ml. Acetonic extract had an LC₅₀ value of 4.148 μg/ml, hydroethanolic extract had 76.09 μg/ml, and aqueous extract had 42.61 μg/ml. All extracts showed the antibacterial activity against Gram-positive bacteria (B. cereus and S. aureus) and a fungal organism, C. albicans. The extracts showed no antibacterial effect on the Gram-negative bacterial strains (P. aeruginosa and E. coli) at a concentration of 250 mg/ml. The highest antimicrobial activity was demonstrated by the acetonic extract on B. cereus which had an MIC of 10.42 mg/ml and a zone of inhibition of 17.33 ± 0.58 at a concentration of 250 mg/ml.

Conclusion

In this research work, we report that C. dichogamus had the antimicrobial activity confirming the folklore claim. The results made a strong case for isolation of novel anticancer lead compounds.

ent-Clerodane diterpenoids from the stems of Croton krabas

The first phytochemical investigation from the stems of Croton krabas resulted in the isolation of three new ent-clerodane diterpenoids, crotonkrabases A-C (1-3), along with two known compounds, 12-oxohardwickiic acid (4) and crotonpyrone B (5). Their structures were elucidated using extensive spectroscopic methods. The structure of 3 was unambiguously proven by X-ray crystallography. Furthermore, the absolute configurations of compounds 1-3 were identified by NOESY and the comparison of their experimental ECD spectra with those of calculated ECD spectra reported in the literature. Compounds 1, 2, and 5 showed antibacterial activities against two Gram-positive bacteria (Bacillus cereus and Bacillus subtilis); whereas compound 4 exhibited weak antibacterial against B. cereus. In addition, compound 4 showed potent α-glucosidase inhibitory activity, which was lower than the reference standard acarbose.

The drug likeness analysis of anti-inflammatory clerodane diterpenoids

Inflammation is an active defense response of the body against external stimuli. Long term low-grade inflammation has been considered as a deteriorated factor for aging, cancer, neurodegeneration and metabolic disorders. The clinically used glucocorticoids and non-steroidal anti-inflammatory drugs are not suitable for chronic inflammation. Therefore, it's urgent to discover and develop new effective and safe drugs to attenuate inflammation. Clerodane diterpenoids, a class of bicyclic diterpenoids, are widely distributed in plants of the Labiatae, Euphorbiaceae and Verbenaceae families, as well as fungi, bacteria, and marine sponges. Dozens of anti-inflammatory clerodane diterpenoids have been identified on different assays, both in vitro and in vivo. In the current review, the up-to-date research progresses of anti-inflammatory clerodane diterpenoids were summarized, and their druglikeness was analyzed, which provided the possibility for further development of anti-inflammatory drugs.