Potential biological applications of bio-based anacardic acids and their derivatives.

Egid Mubofu,Fatma Hamad

doi:10.3390/ijms16048569

Abstract

Cashew nut shells (CNS), which are agro wastes from cashew nut processing factories, have proven to be among the most versatile bio-based renewable materials in the search for functional materials and chemicals from renewable resources. CNS are produced in the cashew nut processing process as waste, but they contain cashew nut shell liquid (CNSL) up to about 30–35 wt. % of the nut shell weight depending on the method of extraction. CNSL is a mixture of anacardic acid, cardanol, cardol, and methyl cardol, and the structures of these phenols offer opportunities for the development of diverse products. For anacardic acid, the combination of phenolic, carboxylic, and a 15-carbon alkyl side chain functional group makes it attractive in biological applications or as a synthon for the synthesis of a multitude of bioactive compounds. Anacardic acid, which is about 65% of a CNSL mixture, can be extracted from the agro waste. This shows that CNS waste can be used to extract useful chemicals and thus provide alternative green sources of chemicals, apart from relying only on the otherwise declining petroleum based sources. This paper reviews the potential of anacardic acids and their semi-synthetic derivatives for antibacterial, antitumor, and antioxidant activities. The review focuses on natural anacardic acids from CNS and other plants and their semi-synthetic derivatives as possible lead compounds in medicine. In addition, the use of anacardic acid as a starting material for the synthesis of various biologically active compounds and complexes is reported.

Highlights

As part of cashew nut processing, the cashew nut shell (CNS) is released to the environment as an agricultural byproduct and waste
These results show that the linear alkyl side chain and the degree of its unsaturation are both required for enhancing the antibacterial activity against S. mutans, whereas the activity against
Cashew nut shells, which are otherwise agrowastes of cashew nut processing factories, upon treatment and refinery, produce cashew nut shell liquid (CNSL),which is a unique source of naturally occurring long-chain hydrocarbon phenols

Summary

Introduction

As part of cashew nut processing, the cashew nut shell (CNS) is released to the environment as an agricultural byproduct and waste. Anacardic acid, which is the major component of natural CNSL, has attracted great research interest due to its biological activities such as antitumor, antioxidant, gastro-protective, and antibiotic It has been used as a synthon for the production of a variety of biologically active compounds with increased efficiency, and some of them outperform their corresponding standard material [9]. The once-thought optimum temperature method of separation by low-pressure distillation leads to the acid thermal decomposition to cardanol, whereas chromatographic methods are not cost effective [13,14,15] Even though it is not green, the most common anacardic acid isolation method used for practical applications is the one reported by Paramashivappa et al [16]. The discussion places strong emphasis on the biological applications of natural anacardic acids and activity-oriented derivatizations into semi-synthetic anacardic acids for the production of improved biologically active compounds

Antibacterial Activity of Anacardic Acids

Anacardic Acids as Antitumor Agents

Anacardic Acidsas Antioxidants

Anacardic Acids as Synthons for Synthesis of Biologically Active Products

Findings

Conclusions