Antibacterial activity of ent -kaurene diterpenoids from Rabdosia rosthornii

Dimeric ent-kauranoids isolated from Isodon japonica var. Glaucocalyx and their anti-inflammatory activities

The phytochemical investigation of the aerial parts of Isodon japonica var. glaucocalyx afforded four undescribed (glaucocalyxin O-R, 1-4) and six known ent-kauranoids (5-10). Their structures were established using NMR and MS measurements. Compounds 1 and 2 are dimeric ent-kaurane-type diterpenoids. Moreover, the plausible biogenetic pathways for compounds 1 and 2 were proposed as Michael addition between two monomers. Eight compounds were assayed for their anti-inflammatory activity by evaluating NO production in LPS-induced RAW 267.4 cells, and compounds 7, 8 and 9 exhibited relatively remarkable anti-inflammatory activities at 10 μM.

Ent-kauranes and ent-atisanes from Euphorbia wallichii and their anti-inflammatory activity

Phytochemical investigation on the whole plant of Euphorbia wallichii led to the identification of twelve diterpenoids, including nine undescribed ones, in which wallkauranes A-E (1-5) were classified as ent-kaurane diterpenoids and wallatisanes A-D (6-9) were assigned as ent-atisane diterpenoids. The biological evaluation of these isolates against NO production was conducted in the LPS-induced RAW264.7 macrophage cells model, resulting in the identification of a series of potent NO inhibitors, with the most active wallkaurane A showing an IC₅₀ value of 4.21 μM. The mechanistic study disclosed that wallkaurane A could inhibit pro-inflammatory cytokines generation such as TNF-α, IL-1β, and IL-6, and decrease the expression of iNOS and COX-2. Wallkaurane A could regulate the NF-κB signaling pathways and the JAK2/STAT3 signaling pathway to suppress the inflammatory reaction in LPS-induced RAW264.7 cells. Meanwhile, wallkaurane A could also inhibit the JAK2/STAT3 signaling pathway, thereby suppressing apoptosis in LPS-induced RAW264.7 cells.

Euphorbia Diterpenes: An Update of Isolation, Structure, Pharmacological Activities and Structure-Activity Relationship

Euphorbia species have a rich history of ethnomedicinal use and ethnopharmacological applications in drug discovery. This is due to the presence of a wide range of diterpenes exhibiting great structural diversity and pharmacological activities. As a result, Euphorbia diterpenes have remained the focus of drug discovery investigations from natural products. The current review documents over 350 diterpenes, isolated from Euphorbia species, their structures, classification, biosynthetic pathways, and their structure-activity relationships for the period covering 2013-2020. Among the isolated diterpenes, over 20 skeletal structures were identified. Lathyrane, jatrophane, ingenane, ingenol, and ingol were identified as the major diterpenes in most Euphorbia species. Most of the isolated diterpenes were evaluated for their cytotoxicity activities, multidrug resistance abilities, and inhibitory activities in vitro, and reported good activities with significant half-inhibitory concentration (IC50) values ranging from 10-50 µM. The lathyranes, isopimaranes, and jatrophanes diterpenes were further found to show potent inhibition of P-glycoprotein, which is known to confer drug resistance abilities in cells leading to decreased cytotoxic effects. Structure-activity relationship (SAR) studies revealed the significance of a free hydroxyl group at position C-3 in enhancing the anticancer and anti-inflammatory activities and the negative effect it has in position C-2. Esterification of this functionality, in selected diterpenes, was found to enhance these activities. Thus, Euphorbia diterpenes offer a valuable source of lead compounds that could be investigated further as potential candidates for drug discovery.

Composition and Antibacterial Screening of the Essential Oils of Leaves and Roots of Espeletiopsis Angustifolia Cuatrec

Hydrodistillation of leaves and roots of Espeletiopsis angustifolia Cuatrec. (Asteraceae) yielded 0.18% and 0.15% essential oils, respectively. GC-MS analysis allowed identification of 24 components, which made up 92.9% of the total oil from the leaves, while only 16 compounds (67.2%) were identified in the roots. The most abundant compounds in the leaves were α-pinene (29.9%), β-caryophyllene (14.1%), α-gurjunene (9.9%), β-pinene (9.6%), and 19-oxo-ent-kaur-16-ene (5.3%). In the roots, the main ones were α-pinene (27.9%), β-pinene (10.9%), β-caryophyllene (10.2%), and bicyclogermacrene (8.6%). Antibacterial activity was tested against Gram-positive and Gram-negative bacteria using the agar diffusion method. Activity was observed only against Gram-positive bacteria. MIC values were determined for Staphyloccocus aureus ATCC 25923 (1000 μg/mL, both roots and leaves) and Enteroccocus faecalis ATCC 29212 (240 μg/mL, roots and 360 μg/ mL, leaves).

Developing an UPLC-MS/MS method to quantify maoecrystal A in rat plasma: Application to a pharmacokinetic study

Maoecrystal A (MC-A) is an ent-kaurane-type diterpene isolated from Rabdosia eriocalyx (Dunn) Hara. MC-A has been reported to show different types of pharmacological activities, including anticancer, anti-inflammatory and bacteriostatic functions. However, bioanalysis of MC-A has not been reported. The purpose of this study is to develop an UPLC-MS/MS method to quantify MC-A in plasma and determine its pharmacokinetic properties using an animal model. The separation was performed using a Waters HSS T3 column (50 mm × 2.1 mm, 1.8 μm, Waters Corp., Milford, MA, USA) with methanol and water containing 0.1% of formic acid as the mobile phases. The mass analysis was performed in a Waters Xevo TQ mass spectrometer using multiple reaction monitoring (MRM) in positive scan mode. Protein precipitation was used to extract the drug from rat plasma samples. The calibration curve is linear in the concentration range 0.49-2000.0 ng/mL. The extraction recovery and the matrix effect were 78.11 to 91.72% and 90.38 to 98.02%, respectively. The RSD of inter/intra-day precisions were <13.72% and the accuracy was >86.41%. Stability studies showed that MC-A was stable (RSD < 14.98%) at different conditions (i.e., short-term, long-term, bench, and three freeze-thaw cycles) in rat plasma. The method was successfully applied to a pharmacokinetic study using rats through oral and intravenous administration routes. The oral bioavailability of MC-A was only 2.9%. Further studies are needed to determine the absorption and metabolism in order to improve the oral bioavailability of MC-A.

ent-6,7-Secokaurane diterpenoids from Rabdosia serra and their cytotoxic activities

Investigation of the hydrophobic extract of Rabdosia serra (Lamiaceae) led to the isolation of seven ent-6,7-secokaurane diterpenoids rabdosins E-K, along with twelve known ent-kaurane diterpenoids. Their structures were established by extensive spectroscopic analysis. The absolute configurations of rabdosins E, F, H and I were determined by single-crystal X-ray diffraction, with rabdosin E having a 3,20-epoxy group. These diterpenoids could be divided into two types according to their skeletons: rabdosins E-J are ent-6,20-epoxy-6,7-secokaur-1,7-olides, and rabdosin K is an ent-6,7-secokaur-7,20-olide. Cytotoxicity evaluation showed that serrin B, serrin A, isodocarpin and lushanrubescensin J exhibited weak to moderate cytotoxic activities (IC50<10μM) against two human cancer cell lines.

New perspectives on antiacne plant drugs: contribution to modern therapeutics

Acne is a common but serious skin disease, which affects approximately 80% adolescents and young adults in 11-30 age group. 42.5% of men and 50.9% of women continue to suffer from this disease into their twenties. Bacterial resistance is now at the alarming stage due to the irrational use of antibiotics. Hence, search for new lead molecule/bioactive and rational delivery of the existing drug (for better therapeutic effect) to the site of action is the need of the hour. Plants and plant-derived products have been an integral part of health care system since time immemorial. Therefore, plants that are currently used for the treatment of acne and those with a high potential are summarized in the present review. Most active plant extracts, namely, P. granatum, M. alba, A. anomala, and M. aquifolium exhibit minimum inhibitory concentration (MIC) in the range of 4-50 µg/mL against P. acnes, while aromatic oils of C. obovoides, C. natsudaidai, C. japonica, and C. nardus possess MICs 0.005-0.6 μL/mL and phytomolecules such as rhodomyrtone, pulsaquinone, hydropulsaquinone, honokiol, magnolol, xanthohumol lupulones, chebulagic acid and rhinacanthin-C show MIC in the range of 0.5-12.5 μg/mL. Novel drug delivery strategies of important plant leads in the treatment of acne have also been discussed.

Bioactive ent-kaurane diterpenoids from Isodon rosthornii

Isorosthin A (1), the first 20-nor-enmein-type diterpenoid, and 15 new ent-kauranoids, isorosthins B-P (2-16), along with 22 known analogues were isolated from the aerial parts of Isodon rosthornii. The structures of 1-16 were elucidated by means of spectroscopic analysis. The relative configuration of 2 and the absolute configuration of 3 were determined by single-crystal X-ray diffraction. Cytotoxicity evaluation against five human tumor lines showed inhibitory effects by several of the compounds tested. Furthermore, 12 of the isolates exhibited inhibitory activity against nitric oxide production in LPS-activated RAW264.7 macrophages.

An ent-kaurane-type diterpene in Croton antisyphiliticus mart

Croton antisyphiliticus is a medicinal plant widely used in the treatment of microbial infections, especially those affecting the genital tract. Crude extract, fractions and pure compound isolated from roots of this species were investigated to validate their antimicrobial activity against Escherichia coli and Staphylococcus aureus. The compound ent-kaur-16-en-18-oic acid was isolated as a major component (0.7% of crude extract), and its MIC value determined against S. aureus (ATCC 6538) was 250 μg/mL. This is the first phytochemical work on the species monitored with antimicrobial assay.

Isorosthornins A-C, new ent-kaurane diterpenoids from Isodon rosthornii

Three new ent-kauranoids, isorosthornins A-C (1–3), and a new natural product, dihydroponicidin (4), together with five known ones were isolated from the aerial parts of Isodon rosthornii. The structures were determined by means of extensive spectroscopic analysis. All diterpenoids isolated were evaluated for their cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cell lines, and compounds 5 and 7 showed significant inhibitory effects on all cell lines.

Antibacterial abietane-type diterpenoid, taxodone from Metasequoia glyptostroboides Miki ex Hu

In an attempt to isolate bioactive constituents, ethyl acetate cone extract of Metasequoia glyptostroboides was subjected to a column chromatographic analysis that resulted in isolation of an abietane-type diterpenoid, taxodone. Its structure was elucidated by spectroscopic means. Further, taxodone showed potential antibacterial effect as diameters of zones of inhibition against foodborne pathogenic bacteria, such as Listeria monocytogenes ATCC 19166, Salmonella typhimurium KCTC 2515, S. enteritidis KCTC 2021, Escherichia coli ATCC 8739, E. coli O157:H7 ATCC 43888, Enterobacter aerogenes KCTC 2190, Staphylococcus aureus ATCC 6538 and S. aureus KCTC 1916, were found in the range of 9.4 to 14.2 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of taxodone against the employed bacterial pathogens were found in the range of 250 to 1000 and 250 to less than 2000 microg/ml, respectively. Also the compound had a strong antibacterial effect on the viable counts of the tested bacteria. These findings indicate that the bioactive compound taxodone present in M. glyptostroboides could be used as an antibacterial agent in food industry to inhibit the growth of certain important foodborne pathogens.

Structure-mutagenicity relationship of kaurenoic acid from Xylopia sericeae (Annonaceae)

Kaurane diterpenes are considered important compounds in the development of new highly effective anticancer chemotherapeutic agents. Genotoxic effects of anticancer drugs in non-tumour cells are of special significance due to the possibility that they induce secondary tumours in cancer patients. In this context, we evaluated the genotoxic and mutagenic potential of the natural diterpenoid kaurenoic acid (KA), i.e. (-)-kaur-16-en-19-oic acid, isolated from Xylopia sericeae St. Hill, using several standard in vitro and in vivo protocols (comet, chromosomal aberration, micronucleus and Saccharomyces cerevisiae assays). Also, an analysis of structure-activity relationships was performed with two natural diterpenoid compounds, 14-hydroxy-kaurane (1) and xylopic acid (2), isolated from X. sericeae, and three semi-synthetic derivatives of KA (3-5). In addition, considering the importance of the exocyclic double bond (C16) moiety as an active pharmacophore of KA cytotoxicity, we also evaluated the hydrogenated derivative of KA, (-)-kauran-19-oic acid (KAH), to determine the role of the exocyclic bond (C16) in the genotoxic activity of KA. In summary, the present study shows that KA is genotoxic and mutagenic in human peripheral blood leukocytes (PBLs), yeast (S. cerevisiae) and mice (bone marrow, liver and kidney) probably due to the generation of DNA double-strand breaks (DSB) and/or inhibition of topoisomerase I. Unlike KA, compounds 1-5 and KAH are completely devoid of genotoxic and mutagenic effects under the experimental conditions used in this study, suggesting that the exocyclic double bond (C16) moiety may be the active pharmacophore of the genetic toxicity of KA.

Chemical Composition of the Essential Oil from Carramboa pittieri (Cuatrec.) Cuatrec. (Asteraceae)

The essential oil from the leaves of Carramboa pittieri (Cuatrec.) Cuatrec. was isolated by hydrodistillation, yielding 0.1%. The chemical composition was determined by GC-FID and GC-MS. Forty-one components were identified by comparison of their mass spectra with Wiley and NIST Library data. The major constituents of the oil were germacrene-D (28.9%), ent-kaur-16-en-19-al (15.1%), β-selinene (8.2%), β-caryophyllene (6.1%) and α-copaene (5.1%).

Kaurene diterpenes from Laetia thamnia inhibit the growth of human cancer cells in vitro

Four ent-kaurene diterpenes were isolated from the leaves of Laetia thamnia L.: ent-kaur-16-en-19-oic acid (1a), ent-3beta-hydroxykaur-16-ene (2), ent-kaur-16-en-3alpha,19-diol (3a), and ent-17-hydroxykaur-15-en-19-oic acid (4). The methyl ester (1b) of compound 1a and the acetate diester (3b) of compound 3a were prepared, and all compounds were evaluated for cytotoxicity against human prostate (22Rv1, LNCaP), colon (HT29, HCT116, SW480, SW620), and breast (MCF-7) tumor cells at concentrations ranging from 6 to 50microg/mL. The kaurenes showed activity in all cell lines tested, with the prostate cells demonstrating the most sensitivity as follows: 22 Rv1 cells towards 1a (IC(50) 5.03microg/mL) and 1b (IC(50) 6.81microg/mL), and LNCaP towards 2 (IC(50) 12.83microg/mL) and 4 (IC(50) 17.63microg/mL).

Diterpenoids from Isodon species and their biological activities

Isodon species (Labiatae) are widely distributed plants, many of which are used in folk medicine. Over the past twenty years, they have received considerable phytochemical and biological attention. Thestructures of their many diterpenoids constituents, especially those with an ent-kaurane skeleton, have been elucidated. The significant phytochemical and pharmacological diterpenoids form the subject of this review. There are 290 references.