Micromorphology and Chemical Studies on Anacardium occidentale L. Stem Bark as an Herbal Medicine

The red and white types of Anacardium occidentale L. stem barks (AoB) are used in the Community of Portuguese Language Countries, including Portugal, to make traditional herbal preparations for the treatment of diabetes. This work aims to obtain the macroscopic, micromorphological, chemical, and purity data necessary to use both types of AoBs as medicinal plants safely. Macroscopically, a brown inner (red AoB) or a dark-brown inner surface (white AoB) was observed. Light and scanning electron microscopy showed that sclereid cells with thin cell walls were significantly larger (p < 0.001) in red AoB than in white AoB, but calcium oxalate druses and starch grain areas were significantly larger (p < 0.001) in white AoB than in red AoB. The chromatographic profiles (thin-layer chromatography and high-performance liquid chromatography) of both types of AoBs were characterized by the presence of gallic and protocatechuic acids and other phenolic derivatives. The condensed tannins were the major secondary metabolites class (143.69 ± 4.67 mg and 73.79 ± 4.46 mg catechin equivalents/g AoB in red and white types, respectively). The loss on drying and the total ash were, respectively, 7.07 ± 0.16% and 2.31 ± 0.18% in red AoB and 6.58 ± 0.16% and 1.94 ± 0.14% in white AoB. The obtained data are helpful in ensuring the quality of AoB as raw material for the pharmaceutical market.