Metal-catalysed C–H bond functionalisation has had a significant impact on how chemists make molecules. Translating the methodological developments to their use in the assembly of complex natural products is an important challenge for the continued advancement of chemical synthesis. In this tutorial review, we describe selected recent examples of how the metal-catalysed C–H bond functionalisation has been able to positively affect the synthesis of natural products.

Recent developments in natural product synthesis using metal-catalysed C–H bond functionalisation

Plant extracts for the control of bacterial growth: efficacy, stability and safety issues for food application.

Studies on the antioxidant activity of Indian Laburnum (Cassia fistula L.): a preliminary assessment of crude extracts from stem bark, leaves, flowers and fruit pulp

As part of ongoing research on cancer chemopreventive agents from botanical dietary supplements, Garcinia mangostana L. (commonly known as mangosteen) was selected for detailed study. Repeated chromatography of a CH2Cl2-soluble extract of the pericarp led to the isolation of two new highly oxygenated prenylated xanthones, 8-hydroxycudraxanthone G (1) and mangostingone [7-methoxy-2-(3-methyl-2-butenyl)-8-(3-methyl-2-oxo-3-butenyl)-1,3,6-trihydroxyxanthone, 2], together with 12 known xanthones, cudraxanthone G (3), 8-deoxygartanin (4), garcimangosone B (5), garcinone D (6), garcinone E (7), gartanin (8), 1-isomangostin (9), α-mangostin (10), γ-mangostin (11), mangostinone (12), smeathxanthone A (13), and tovophyllin A (14). The structures of compounds 1 and 2 were elucidated by spectroscopic data analysis. Except for compound 2, which was isolated as a minor component, the antioxidant activities of all isolates were determined using authentic and morpholinosydnonimine-derived peroxynitrite methods, and comp...

/pdf/antioxidant-xanthones-from-the-pericarp-of-garcinia-4y9pfpqh0g.pdf

Antioxidant Xanthones from the Pericarp of Garcinia mangostana (Mangosteen)

Phloroglucinol compounds of natural origin

Antioxidant xanthones from Garcinia subelliptica

A higher concentration of kinsenoside, 3-(R)-3-β-D-glucopyranosyloxybutanolide (1), was detected in the crude drug Anoectochilus formosanus, and A. koshunensis by HPLC analysis. A methylation reaction occurred to give methyl ester (4) when the lactone ring of 1 was cleaved by silica gel catalysis using methanol containing solvent used in the purification step resulting in difficulty to purify 1. To avoid the cleavage reaction, a reversed-phase or silica gel column without methanol was used to give a high yield of 1. In an anti-hyperliposis assay using high-fat diet rats, 1 significantly reduced the weights of body and liver, and also decreased the triglyceride level in the liver compared to those of control rats. On the other hand, the epimer of 1, 3-(S)-3-β-D-glucopyranosyloxybutanolide (2), trivially named goodyeroside A, which was isolated from Goodyera species, had no effect for anti-hyperliposis. In aurothioglucose-induced obese mouse, 1 suppressed the body and liver weight increase, significantly ameliorated the triglyceride level in the liver, and also reduced the deposition of uterine fat-pads.

Higher yielding isolation of kinsenoside in Anoectochilus and its antihyperliposis effect.

Two new xanthones, garciniaxanthone D (1) containing a dihydrobenzofuran ring and 1,4,5-trihydroxyxanthone (2), have been isolated from Garcinia subelliptica as superoxide anion scavengers. Their structures have been determined mainly by spectroscopic methods and some chemical reactions.

Novel xanthones with superoxide scavenging activity from garcinia subelliptica

The anti-inflammatory activities of alpha-truxillic acid (1) and 4,4'-dihydroxy-alpha-truxillic acid (2) as well as their monomer components (E)-cinnamic acid (3) and (E)-p-coumaric acid (4) were evaluated in the formalin test. alpha-Truxillic acid (1) and its derivative 4,4'-dihydroxy-alpha-truxillic acid (2) exhibited significant activity against inflammatory pain response, while their monomer components (E)-cinnamic acid (3) and (E)-p-coumaric acid (4) did not show any activity against either neurogenic or inflammatory pain responses induced by formalin in mice. These results suggested that the dimeric structure might play an important role for the expression of anti-inflammatory activity. Furthermore, in order to gain information on their potencies, their anti-inflammatory activities were compared with that of incarvillateine (5) which contains the same dimeric structure and showed more potent antinociceptive activity than morphine in the formalin test. The activities of alpha-truxillic acid (1) and 4,4'-dihydroxy-alpha-truxillic acid (2) at the dose of 40 mg/kg against inflammatory pain response were equal to that of incarvillateine at doses of 20 mg/kg.

Toyokichi Yoshizawa

Papers

Antioxidant xanthones from Garcinia subelliptica

Higher yielding isolation of kinsenoside in Anoectochilus and its antihyperliposis effect.

Novel xanthones with superoxide scavenging activity from garcinia subelliptica

Anti-inflammatory Activities of α-Truxillic Acid Derivatives and Their Monomer Components

Butanoic acid glucoside composition of whole body and in vitro plantlets of Anoectochilus formosanus