New Cytotoxic Seco-Type Triterpene and Labdane-Type Diterpenes from Nuxia oppositifolia

Abstract

Chromatographic purification of the n-hexane and dichloromethane extracts of Nuxia oppositifolia aerial parts, growing in Saudi Arabia, resulted in the isolation and characterization of three new labdane-type diterpene acids, 2β-acetoxy-labda-7-en-15-oic acid (1), 2β-acetoxy-7-oxolabda-8-en-15-oic acid (2), 2β-acetoxy-6-oxolabda-7-en-15-oic acid (3), and one new seco-triterpene, 3,4-seco olean-12-en-3,30 dioic acid (4), together with 10 known lupane, oleanane and ursane-type triterpenes, as well as the common phytosterols, β-sitosterol and stigmasterol (5–16). Their structures have been assigned on the basis of different spectroscopic techniques including 1D and 2D NMR. Moreover, 13 of the isolated compounds were tested on the human cancer cell lines HeLa (cervical), A549 (lung) and MDA (breast), and most of the compounds showed potent cytotoxic activities in vitro.

Alpha-Amylase and Alpha-Glucosidase Enzyme Inhibition and Antioxidant Potential of 3-Oxolupenal and Katononic Acid Isolated from Nuxia oppositifolia

“…However, in recent times, the full potential of N. oppositifolia has not been utilized due to the lack of scientific proof. Previously, our group has isolated various bioactive compounds from the methanolic extract of aerial parts of N. oppositifolia [11]. In this study, we performed an activity-guided screening and isolation of bioactive compounds from different fractions of N. oppositifolia.…”

“…The n-hexane fraction (17.6 g) showed maximum activity, and was further fractionated using a pre-packed silica gel column (40 mm i.d. × 350 mm) and eluted with n-hexane-ethyl acetate gradient, following the method described in Al-Massarani et al (2017) [11]. The collected fractions were examined with thin-layer chromatography (TLC) and similar fractions were pooled together into four different sub-fractions (A-D).…”

“…The aerial parts of N. oppositifolia (900 g) were dried, powdered, and then extracted three times with 80% methanol as described earlier [11]. The extracts were filtered and concentrated under reduced pressure at 40 • C using a rotary vacuum evaporator (Buchi, New Castle, PA, USA).…”

“…The sub-fractions were tested for α-amylase and α-glucosidase inhibitory activity; the sub-fraction (A and B) which showed the highest inhibition was further analyzed. Sub-fraction A which was eluted with 5% EtOAc/n-hexane, was further purified using a Chromatotron device) (San Bruno, CA, USA) (0.5% EtOAc/n-hexane) to yield 3-oxolupenal (170 mg), as described by Al-Massarani et al (2017) [11]. Similarly, sub-fraction B which was eluted with 10% EtOAc/n-hexane gave katononic acid (153 mg) upon crystallization.…”

“…The phytochemical analysis of Nuxia plants has shown that they are a rich source of phenylpropanoid glycosides such as verbascoside [10], clerodane and labdane diterpenoids and pentacyclic triterpenes [8]. Recently, Al-Massarani et al (2017) reported the isolation of three new labdane diterpenoic acids, a new seco-triterpene (3,4-seco-olean-12-en-3,30 dioic acid) along with some known triterpenes (3-oxolupenal and katononic acid) and phytosterols such as β-sitosterol and stigmasterol [11]. Many studies have suggested the use of triterpenes in the prevention of diabetic complications such as nephropathy, embryopathy, neuropathy, or impaired wound healing [12].…”