Structural Studies on Three Plant Diterpenoids from Leonotis nepetaefolia

Abstract

This paper describes the interesting structural studies on three new diterpenoids (plant products), namely, hydroxy‐dialactone nepetaefolinol (9,13‐epoxy‐6β‐hydroxy‐8α‐labdane‐16,15 :19,20‐diolactone), dehydrated nepetaefolinol (9,13‐epoxylabd‐5‐ene‐16,15:19,20‐diolactone) and isomeric tetrol (15,16‐epoxy‐labda‐13(16),14‐diene‐6β,9,17,19‐tetrol: which is the reduction product of new diterpenoid leonotinin) isolated from Indian herbal plant Leonotis nepetaefolia (collected in the flowering season from Guindy area, Madras), and are found to be the major compounds in their extractions, so they are expected to possess the interesting pharmacological properties. In all three structures, the fused ring systems adopt distorted chair‐chair, distorted chair and intermediate between 1,2‐diplanar and half‐chair and chair‐chair conformations. In compounds 1 and 2, the twisted form of lactone rings are orthogonal to each other and make dihedral angle of 88.4(1) and 87.5(2)° with each other. The primary interaction between the molecules is van der Waal's in nature.

Marrubiin

“…According to the recent literature [38], the detection of marrubiin in fresh plant material has been reported, together with the isolation of pre-furanic mixed with non-related furanic labdanoids [44,45,46,47], and these data indicate the existence of marrubiin as a natural compound inside the living organism and as an end product of a biosynthetic pathway. The transformation of premarrubiin into marrubiin is indicative of the comparative instability of the former compound to the more stable furanic form.…”

“…The transformation of premarrubiin into marrubiin is indicative of the comparative instability of the former compound to the more stable furanic form. Generally, under certain conditions the chemical treatment of 9,13–15,16-diepoxylabdane derivatives can converted them into the more stable furanic form, and no work has been done to study the effect of other substitution patterns in the C 11,12 and C 14-17 systems, however, many prefuranic structures have been isolated without their corresponding furanic forms [44,45,46,47]. The relation between premarrubiin and marrubiin needs to be investigated in the plant tissues using one of the available advanced techniques like high field solid-state NMR.…”

Leonotis nepetifolia Protects against Acetaminophen-Induced Hepatotoxicity: Histological Studies and the Role of Antioxidant Enzymes

“…Several compounds such as diterpenes, glycosidic iridoids, stigmasterol, flavonoids and tannins have been isolated from the leaves of L. nepetifolia [11][12][13]. Additionally, actesoide, martinoside and lavandulipolioside have also been isolated in the stems and these compounds have been shown to possess potent antioxidant activity [14].…”

Bis-spirolabdane Diterpenoids from Leonotis nepetaefolia

“…In addition, a variety of biological activities including antispasmodic, antibacterial, antifungal, , anti-inflammatory, antioxidative, , antiasthmatic, and antidiarrheal activities have been reported for the crude extracts or pure compounds from this plant. Previous phytochemical studies of the plant indicated the presence of labdane diterpenoids, ,,− iridoids, , and coumarins . As part of an ongoing effort to search for bioactive constituents from psychoactive plants, CH 2 Cl 2 -MeOH (1:1) extract of the leaves of L .…”