Two New Dolabrane Diterpenes from the Chinese Mangrove Ceriops tagal

New Diterpenes with Potential Antitumoral Activity Isolated from Plants in the Years 2017-2022

Diterpenes represent a wider class of isoprenoids, with more than 18,000 isolated compounds, and are present in plants, fungi, bacteria, and animals in both terrestrial and marine environments. Here, we report on the fully characterised structures of 251 new diterpenes, isolated from higher plants and published from 2017, which are shown to have antitumoral activity. An overview on the most active compounds, showing IC50 < 20 μM, is provided for diterpenes of different classes. The most active compounds were extracted from 29 different plant families; particularly, Euphorbiaceae (69 compounds) and Lamiaceae (54 compounds) were the richest sources of active compounds. A better activity than the positive control was obtained with 33 compounds against the A549 cell line, 28 compounds against the MCF-7 cell line, 9 compounds against the HepG2 cell line, 8 compounds against the Hep3B cell line, 19 compounds against the SMMC-7721 cell line, 9 compounds against the HL-60 cell line, 24 compounds against the SW480 cell line, and 19 compounds against HeLa.

Dolabrane-Type Diterpenoids with Immunosuppressive Activity from Koilodepas hainanense

Thirteen new dolabrane-type diterpenoids, koilodenoids A-M (1-13), including a chlorinated congener (2), along with six known analogues, were isolated from Koilodepas hainanense. The structures were determined by analysis of spectroscopic data, ECD spectra, and X-ray crystallographic studies. The absolute configuration of C-15 in the 15,16-diol unit of compounds 4 and 5 was established by using the dimolybdenum tetraacetate [Mo₂(AcO)₄]-induced ECD method. Compounds 4, 7, 16, 17, and 19 showed moderate to significant immunosuppressive activities against the proliferation of T and B lymphocytes in vitro, with compound 16 being the most potent (IC₅₀ 0.86 and 0.29 μM, respectively).

Bioassay Directed Fractionation of Petroleum Ether Extract of Aerial Parts of Ceriops tagal: Isolation of Lupeol as the Nematicidal Agent against Cyst Nematode Heterodera zeae

Plant parasitic cyst nematode  Heterodera zeae  is a pest, causing substantial economic losses in agriculture. Organic pesticides, based on plant products have emerged as eco-benign nematicidal agents.  Ceriops tagal  is a well-known marine medicinal plant which has not been evaluated against any nematode. Petroleum ether extract of the aerial parts of the plant (CTP), exhibited promising activity against infective stage larvae of  H. zeae . On subjecting to classical solvent-solvent separation, it afforded petroleum ether soluble (CTP-S), methanol soluble ( CTPMS-1 , CTPMS-2) and insoluble (CTPM-IN-2) fractions, which exhibited activity against the cyst nematode within 24 h exposure. GC, GCMS and ESI-HRMS analyses of CTPMS-1 and CTPMS-2 fractions resulted in the identification of a number of compounds, including pentacyclic triterpenoids, lupeol ( 1 ), betunal ( 2 ), betulin ( 3 ), lupenone ( 4 ), betulonaldehyde ( 5 ), betulonic acid ( 7 ), methyl-3-acetoxy-27- O -(3,4-dihydroxy- E -cinnamoyl)-20(29)-lupen-28-oate ( 8 ) and  β -amyrin, along with phenylpropanoid esters, fatty acids and their derivatives, benzamide, and indole derivatives. CTPM-IN-2 which mainly contained lupeol ( 1 ) exhibited maximum nematicidal activity, with 91% and 93% mortality of the larvae of  H. zeae , after exposure for 72 h at the concentration of 0.5% and 1%, respectively. Its fractionation and purification through column chromatography resulted in the isolation and identification of four lupane-type triterpenoids  1 ,  3 ,  4  and betulinic acid ( 6 ). One of its most abundant column fractions CC-9-18 (145 mg) which exhibited substantial activity, with 81% mortality at the lowest concentration of 0.125% after 48 h of incubation mainly contained lupeol. It seems lupeol, a wide spread bio-privileged triterpenoid is the nematicidal principle of the plant as its authentic sample showed LC 50 value of 0.061 after 72 h exposure. It is for the first time that nematicidal activity is reported for any part of  C. tagal  and that of lupeol against  H. zeae.  Pentacyclic triterpenoids  1 - 8  are biosynthetically related. Of the twenty-four compounds isolated or identified in the present investigation only five constituents  1 ,  3 ,  6 ,  7  and palmitic acid have been isolated previously from  C. tagal .

Dolabrane Diterpenoids from the Chinese Liverwort Notoscyphus lutescens

Nine new dolabrane-type diterpenoids, notoscarins A-I (1-9), including an unprecedented 6,18-cyclo-dolabrane-type diterpenoid (1) obtained through intramolecular cyclization, two rare 19-nor-2-chloro-dolabrane diterpenoids (2 and 3), six new related dolabrane-type diterpenoids (4-9), and one new butyrolactone derivative (10), were isolated from the Chinese liverwort Notoscyphus lutescens. The 6,18-cyclo-dolabrane and 19-nor-dolabrane carbon skeletons are reported for the first time. The structures of these compounds were determined on the basis of MS and NMR spectroscopic data, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Preliminary bioassays showed that compounds 1-10 exhibited moderate to weak quinone reductase-inducing activity in Hepa-1c1c7 cells.

Evaluation of Antioxidant and Anticorrosive Activities of Ceriops tagal Plant Extract

Mangroves are plants known for their various medicinal and economical values, and therefore are widely investigated for their phytochemical, antioxidant, antidiarrheal, and antimicrobial activities. In the present study, we analyze the antioxidant and anticorrosive properties of Ceriops tagal (C. tagal), a tropical and subtropical mangrove plant of the Rhizophoraceae family. The total phenolic content (TPC) and total flavonoid content (TFC) were found to be 101.52 and 35.71 mg/g, respectively. The extract (100 µg/mL) exhibited 83.88, 85, and 87% antioxidant property against 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide, and hydrogen peroxide free radicals. In addition, 600 ppm of C. tagal extract showed 95% corrosion inhibition against 1 M HCl attack on mild steel at 303 ± 1 K, which declined over other concentrations and temperatures, where AAS produced 82% inhibition at 600 ppm. UV-visible spectroscopy analysis revealed the formation of an inhibitor metal complex. The elemental analysis provided the presence of 84.21, 9.01, and 6.37% of Fe, O, and C, respectively, in inhibited mild steel, whereas the same were 71.54, 22.1, and 4.34%, respectively, in uninhibited specimen, stressing the presence of protective film on the metal surface. Scanning electron microscopy (SEM) also showed some noteworthy changes in both uninhibited and inhibited mild steel, making C. tagal plant a better alternative than any other synthetic inhibitors. Further, the atomic force microscopy (AFM) surface topography analysis showed that 600 ppm of C. tagal extract significantly diminished corrosion on the surface of mild steel.