Isomeric ent‐Labdane‐Type Diterpenoids from the Stems of Rhizophora mucronata

Abstract

Two new constitutional isomers of ent‐labdane‐type diterpenoids, 1 and 2, with an unusual seven‐membered lactone moiety (i.e., 1), together with two known compounds, 3 and 4, were isolated from the acetone extract of Rhizophora mucronata. Their structures were elucidated as rhizomucronol A and B (1 and 2, resp.) by spectroscopic analyses and chemical evidence. The absolute configuration of 2 was established by applying the Mosher ester procedure.

Phytochemicals from Rhizophora mucronata Propagules, Its In Vitro Anti-Cancer and In Silico Drug-Likeness Potential

“…Triterpenoids (3β-O-(E)-(4-methoxy) cinnamoyl-15 α-hydroxyl β-amyrin, adian-5-en 3-ol and lupeol) have been isolated from the chloroform extract of the stem bark [19]. Diterpenoids (rhizomucronol A and B) have been isolated from the acetone extract of the stem [20]. Extracts from the bark of R. mucronata have anti-diabetic (inhibition of the α-glucosidase enzyme) effect [21], moderate antibacterial effects against Escherichia coli and Staphylococus epidermidis [22], and antiplasmodial activities [18].…”

Diterpenoids of terrestrial origin

“…Ring A has also been oxidized to a lactone in rhizomucronol A 5 which is a constituent of the South-East Asian medicinal plant Rhizophora mucronata (Rhizophoraceae). 29 Andrographolide has continued to attract interest as a tumour inhibitory agent. It has been reviewed, 30 more relatives have been isolated 31 from Andrographis paniculata and its biological activity has been examined further.…”

Epimeric Excolides from the Stems of Excoecaria agallocha and Structural Revision of Rhizophorin A

“…Mangroves particularly those of the genus Excoecaria have been recognized as a rich source of diterpenoids of structural diversity possessing a wide range of biological activities. , Of the diterpenes from the genus Excoecaria , most are derived from unusual assemblages with diverse classes such as labdanes, pimaranes, beyeranes, and kauranes. , As part of our ongoing research program on bioactive compounds from the Indian mangrove flora, − we have recently examined the acetone extract of the stems of Excoecaria agallocha , which resulted in the isolation of four new 2,3-secolabdanoids with an unprecedented skeleton: epimeric excolides A ( 1 – 3 ) and excolide B ( 4 ) along with two known compounds (Figure ). The known compounds were characterized as excoecarin D ( 5 ) and agallochin I ( 6 ) by comparison of their physical and spectroscopic data (MS, 1 H and 13 C NMR) with reported data. , …”

“…Their structures were determined by spectroscopic analysis, chemical modifications, CD, and single-crystal X-ray analysis (1 and 4) as excolide A (1), 11-epi-excolide A (2), 11,13-di-epi-excolide A (3), and excolide B (4). In addition, the structure of rhizophorin A (7), a novel bicyclic secolabdanoid, was revised as excolide A (1).…”