Synthesis of (−)-Pinellic Acid and Its (9R,12S,13S)-Diastereoisomer

The Octadecanoids: Synthesis and Bioactivity of 18-Carbon Oxygenated Fatty Acids in Mammals, Bacteria, and Fungi

The octadecanoids are a broad class of lipids consisting of the oxygenated products of 18-carbon fatty acids. Originally referring to production of the phytohormone jasmonic acid, the octadecanoid pathway has been expanded to include products of all 18-carbon fatty acids. Octadecanoids are formed biosynthetically in mammals via cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) activity, as well as nonenzymatically by photo- and autoxidation mechanisms. While octadecanoids are well-known mediators in plants, their role in the regulation of mammalian biological processes has been generally neglected. However, there have been significant advancements in recognizing the importance of these compounds in mammals and their involvement in the mediation of inflammation, nociception, and cell proliferation, as well as in immuno- and tissue modulation, coagulation processes, hormone regulation, and skin barrier formation. More recently, the gut microbiome has been shown to be a significant source of octadecanoid biosynthesis, providing additional biosynthetic routes including hydratase activity (e.g., CLA-HY, FA-HY1, FA-HY2). In this review, we summarize the current field of octadecanoids, propose standardized nomenclature, provide details of octadecanoid preparation and measurement, summarize the phase-I metabolic pathway of octadecanoid formation in mammals, bacteria, and fungi, and describe their biological activity in relation to mammalian pathophysiology as well as their potential use as biomarkers of health and disease.

Natural glycosidic antioxidants from Cynanchum atratum roots

Two new rhamnosides, 18-O-α-l-rhamnopyranosylabietic acid (1) and (E)-3,5-dimethoxystilben-4'-O-α-l-rhamnopyranoside (2), five known glucosides (3-7) along with three others were isolated from Cynanchum atratum roots. The structures of new compounds were elucidated by physical data analyses such as NMR, UV, IR, HR-ESI-MS, as well as acid hydrolysis. All of them were assessed for their antioxidant activities through 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical ion (ABTS•⁺), 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH•) and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•) assay, with l-ascorbic acid used as the positive control. As a result, compounds 3-5 exhibited obvious antioxidant activities. These bioactive components could be promising antioxidants.

Efficient and specific conversion of 9-lipoxygenase hydroperoxides in the beetroot. Formation of pinellic acid

The linoleate 9-lipoxygenase product 9(S)-hydroperoxy-10(E),12(Z)-octadecadienoic acid was stirred with a crude enzyme preparation from the beetroot (Beta vulgaris ssp. vulgaris var. vulgaris) to afford a product consisting of 95% of 9(S),12(S),13(S)-trihydroxy-10(E)-octadecenoic acid (pinellic acid). The linolenic acid-derived hydroperoxide 9(S)-hydroperoxy-10(E),12(Z),15(Z)-octadecatrienoic acid was converted in an analogous way into 9(S),12(S),13(S)-trihydroxy-10(E),15(Z)-octadecadienoic acid (fulgidic acid). On the other hand, the 13-lipoxygenase-generated hydroperoxides of linoleic or linolenic acids failed to produce significant amounts of trihydroxy acids. Short-time incubation of 9(S)-hydroperoxy-10(E),12(Z)-octadecadienoic acid afforded the epoxy alcohol 12(R),13(S)-epoxy-9(S)-hydroxy-10(E)-octadecenoic acid as the main product indicating the sequence 9-hydroperoxide → epoxy alcohol → trihydroxy acid catalyzed by epoxy alcohol synthase and epoxide hydrolase activities, respectively. The high capacity of the enzyme system detected in beetroot combined with a simple isolation protocol made possible by the low amounts of endogenous lipids in the enzyme preparation offered an easy access to pinellic and fulgidic acids for use in biological and medical studies.