Quantitative analysis of cashew nut shell liquid and isomeric characterization of its primary constituents: Anacardic Acids, Cardanols, and Cardols

Cashew nut shells are increasingly valued due to the rising production of cashew kernels and the presence of extractives known as cashew nut shell liquid (CNSL). CNSL is rich in phenolic lipids, particularly anacardic acids, cardanols, and cardols, which have potential to replace fossil-based compounds. These substances have diverse applications in the pharmaceutical, chemical, cosmetic, and energy industries. However, the precise composition of CNSL is not fully understood, and there is no published method available for the accurate quantification of anacardic acids, cardanols and cardols (ACC) in cashew nut shells. This article presents an optimized method for the quantitative extraction of maximum CNSL from cashew nut shells, followed by a detailed analysis of the composition of ACC, including its 12 key isomers. The extraction parameters were optimized using a Soxhlet extraction method and acetone as the solvent. The optimal drying temperature was found to be 60 °C, with an extraction time of 12 h, for the greatest yield of extracted material while preventing degradation of anacardic acids in the original CNSL. High-performance liquid chromatography was used to accurately quantify the 12 AAC isomers. The developed method was then used to compare the ACC contents in steam-treated shells resulting from the cashew nut shelling process with the contents in fresh shells. This analytical approach advances our knowledge of the extractives contained in cashew nuts shells thereby paving the way for further investigations and valorization of this abundant resource.