Clerodendrone, a Novel Hydroquinone Diterpenoid from Clerodendrum Indicum

Two pairs of epimers and three undescribed diterpenoids from Pseudocaryopteris paniculata

A phytochemical investigation on the petroleum ether partition of the whole plant of Pseudocaryopteris paniculata, yield seven new compounds: one phytanes diterpenoid (2Z,6E,10E) 14-keto-2,6,10-trimethyl pentadeca-2,6,10-trien-1-carboxylic acid (1), five clerodane diterpenoids: paniculatins A-E (2, 3a/3b, 4a/4b), one abietane diterpenoid: ent-uncinatone (5), together with 12 known compounds. Their structures were elucidated on the basis of 1D and 2D Nuclear Magnetic Resonance （NMR_, Infrared Radiation (IR), and mass spectroscopic data. Compound 2, 5, and 11 showed weak selective cytotoxic activity of 11 human cancer cell lines.

Chemical constituents of Ajuga forrestii and their anti-ferroptosis activity

Six new neoclerodane diterpenoids (1-6), along with ten known compounds (7-16), were isolated from Ajuga forrestii. Their structures were elucidated by HRESIMS, 1D and 2D NMR, ECD calculation, and single-crystal X-ray diffraction analysis. The structure of a known neoclerodane diterpene ajudecunoid C (6) was revised based on the reported NMR empirical rules. All the isolates were evaluated for their inhibitory effect on RSL3-induced ferroptosis in HT22 mouse hippocampal neuronal cells. Among them, compounds 8, 9, and 12 significantly inhibited RSL3-induced ferroptosis with EC₅₀ values of 0.45 μM, 0.076 μM, and 0.14 μM.

Ferroptosis Inhibitory Aromatic Abietane Diterpenoids from Ajuga decumbens and Structural Revision of Two 3,4-Epoxy Group-Containing Abietanes

Two new 3,4-epoxy group-containing abietane diterpenoids (1 and 2), together with five known diterpenoids (3-7), were isolated from Ajuga decumbens. Their structures were elucidated by spectroscopic data analysis, NMR calculations, and X-ray diffraction experiments. The structures of two known abietane diterpenoids were revised based on NMR calculations and X-ray diffraction data. Notably, compound 4 specifically inhibited RSL3-induced ferroptosis with an EC₅₀ of 56 nM by antioxidation. Moreover, 4 significantly decreased RSL3-induced lipid and cytosolic ROS accumulation and ferroptosis marker gene PTGS2 mRNA expression. This work reports the most potent natural inhibitor against ferroptosis found so far.

Antifeedant, cytotoxic, and anti-inflammatory neo-clerodane diterpenoids in the peltate glandular trichomes and fresh leaves of Ajuga forrestii

The Lamiaceae plant Ajuga forrestii Diels is a traditional Chinese herbal medicine with abundant glandular trichomes (GTs), but their chemistry and biological functions remain uninvestigated. Here, a panel of six highly functionalized neo-clerodane diterpenoids was localized to the peltate GTs of A. forrestii using laser microdissection coupled with HPLC analysis, indicating that the GTs of A. forrestii are an excellent material for the elucidation of the yet unclear biosynthetic pathway of natural neo-clerodane diterpenoids. In addition, four undescribed neo-clerodane diterpenoids with an acyclic C-9 side chain including two pairs of 1:1 mixture of inseparable diastereomers, ajuforrestins D-G, were isolated from the fresh leaves of A. forrestii together with six known compounds. The structures of the undescribed compounds were elucidated by spectroscopic (including 1D and 2D NMR and HR-ESI-MS) analyses. Biological assays indicated that the major GT compound ajugacumbin B and undescribed ajuforrestins D/E showed antifeedant activity against Helicoverpa armigera, suggesting that neo-clerodanes in A. forrestii should be involved in plant defence against insects. Moreover, the abietane diterpenoid ajuforrestin B exhibited significant anti-inflammatory activity on the secretion of interleukin-2 (IL-2) and cytotoxicity against three cancer cell lines, NCI-H1975, HepG2 and MCF-7, suggesting that ajuforrestin B could positively contribute to the therapeutic effects of this traditional Chinese medicine.

Diterpenoids from the Whole Plants of Ajuga nipponensis and Their Inhibition of RANKL-Induced Osteoclastogenesis

Two new diterpenoids, ajudecunoid A (1) and ajudecunoid B (14), along with thirteen known diterpenoids, were isolated from the whole plants of Ajuga nipponensis Makino. Their structures were elucidated by the extensive spectroscopic analysis (UV, IR, MS, and NMR). The absolute configurations of ajudecunoid A (1) and ajudecunoid B (14) were defined through analysis of X-ray crystallography. Fifteen compounds were evaluated for inhibition of the formation of osteoclasts in bone marrow-derived macrophages (BMM) cells. Two neo-clerodane diterpenoids ajuganipponin B (5) and (12S)-6α,19-diacetoxy-18-chloro-4α-hydroxy-12-tigloyloxy-neo-clerod-13-en-15,16-olide (12) showed significant inhibition of osteoclastogenesis with IC₅₀ values of 0.88 and 0.79 μM, respectively. Here we firstly reported diterpenoids with anti-osteoclastogenesis activity from A. nipponensis.

19(4→3)-abeo-abietane diterpenoids from Scrophularia dentata Royle ex Benth

Five 19(4→3)-abeo-abietane diterpenoids, scrodentoids A-E (1-5), were isolated from the whole plant of Scrophularia dentata. Planar structures of scrodentoids A-E were elucidated mainly by using 1D, 2D NMR and MS data. The absolute configurations of compounds 1 and 2 were established using X-ray crystallographic analysis. The absolute configurations of other compounds were confirmed using HPLC-UV/CD detection. The immunosuppressive effects of compounds 1-5 were studied using a ConA-induced splenocyte proliferation model. These compounds significantly inhibited ConA-induced splenocyte proliferation, with IC50 values in the range of 3.49-133.86 μM. Compounds 1-5 (IC50>10 μM) showed no discernible cytotoxic activity against B16 or MCF-7 cells.

Rearranged abietane diterpenoids from the roots of Clerodendrum trichotomum and their cytotoxicities against human tumor cells

The roots of the medicinal ornamental plant Clerodendrum trichotomum yielded a series of rearranged abietane diterpenoids, including three 17(15→16)-abeo-abietane (1-3) and three 17(15→16),18(4→3)-diabeo-abietane (4-6) derivatives. Their structures were elucidated by means of spectroscopic methods. The absolute configuration of (10R,16R)-12,16-epoxy-11,14,17-trihydroxy-6-methoxy-17(15→16)-abieta-5,8,11,13-tetraene-7-one (1) was deduced by a combination of single crystal X-ray diffraction analysis and the observed Cotton effects in its circular dichroism (CD) spectrum. All isolates were tested for their cytotoxicities against five human cancer cell lines (BGC-823, Huh-7, KB, KE-97, and Jurkat). Among them, compounds 4, 6, 9, 10, 12, and 14, each possessing a common 17(15→16),18(4→3)-diabeo-abietane framework, were found to have remarkable cytotoxic effects with IC50 values ranging from 0.83 to 50.99 μM.

Phytochemical investigation and in vitro antinociceptive activity of Clerodendrum indicum leaves

The crude ethanolic extracts of Clerodendrum indicum Linn. leaves were investigated for possible antinociceptive activity using acetic acid induced writhing model in mice. Phytochemical analysis was also carried out according to the standard procedures to identify the presence of different phytoconstituents in the ethanolic extract of the plant leaves. The study results showed 38.91 and 55.24% inhibition of writhings in the tested mice when ethanolic extract of Clerodendrum indicum Linn. leaves at doses of 250 and 500 mg kg(-1) body weight was given intraperitoneally, respectively. The study results were also compared with antinociceptive activity of the standard drug, Diclofenac sodium (68.37% inhibition) used at 25 mg kg(-1) body weight. At the above doses, the crude ethanolic extract of the plant showed significant antinociceptive activity in dose dependent fashion in acetic acid-induced writhing model in mice. The inhibition of writhings was calculated in respective to control group and it was found that p-values (<0.0001) obtained in all cases were extremely statistically significant. However, the phytochemical analysis showed the presence of alkaloid, steroid, saponin, tannin, reducing sugar and gum. The results suggest that crude ethanolic extracts of Clerodendrum indicum leaves possess significant antinociceptive properties justifying its folkloric use as analgesics and further research is necessary to isolate the principle phytochemical constituent(s) responsible for this activity.

A New Abietane Diterpenoid from Clerodendrum Kaichianum Hsu

A new abietane diterpenoid has been isolated from Clerodendrum kaichianum Hsu and characterised as 11-methoxyl-12,14-dihydroxy-13-(2-hydroxypropyl)-3,5,8,11,13-abietapentaen-7-one. Its structure was established by spectroscopic analysis, including 2D NMR.