Synthesis and biological activities of anacardic acid and cardanol derivatives from cashew nut shell liquid

Abstract

Cashew nut shell liquid (CNSL) contains three mixtures of anacardic acid 1 (major), and cardanol 2 and cardol 3. The separation of these mixtures by semi-prep HPLC furnished nine compounds which were subsequently subjected to anti-inflammatory and antioxidant activity tests. Both anacardic acid 1 and cardanol 2 displayed no cytotoxicity, while cardol 3 revealed cytotoxicity at 50 µM on Raw 264.7 cells. Anacardic acid C15:3 7 exhibited the highest reducing NO production by 71% at 100 µM. For antioxidant assay, anacardic acid 5-7 and cardol 14-15, and their hydrogenated compounds, 4 and 12 could scavenge superoxide anion radicals by PMS-NADH. The antioxidant activity of anacardic acid was found to depend on the number of double bond on side chain. Anacardic acid 1 and cardol 3 were bactericidal agents for Propionibacterium acnes KCCM 41747 and bacteriostatic agents for Streptococcus mutans ATCC 25175, Streptococcus sobrinus KCCM 11898, Staphylococcus aureus ATCC 25923 and Salmonella typhi ATCC 422. Twenty anacardic acid and twelve cardanol derivatives were synthesized. Among them, twenty-five compounds have not been reported. The ester and ether derivatives of anacardic acid 35-42 could also display scavenging superoxide anion radicals by PMS-NADH, particularly anacardic acids ester 37 and ether 42 with eight carbon atoms. Additionally, anacardic acid 32, 35, 39-40 displayed good to excellent antibacterial activity against tested bacteria. Cardanol thiosemicarbazide 53 showed very good activity against S. sobrinus.