Postharvest Drying Techniques Regulate Secondary Metabolites and Anti-Neuroinflammatory Activities of Ganoderma lucidum

Ganoderma lucidum extract is a potent traditional remedy for curing various ailments. Drying is the most important postharvest step during the processing of Ganoderma lucidum. The drying process mainly involves heat (36 h at 60 degrees C) and freeze-drying (36 h at -80 degrees C). We investigated the effects of different postharvest drying protocols on the metabolites profiling of Ganoderma lucidum using GC-MS, followed by an investigation of the anti-neuroinflammatory potential in LPS-treated BV2 microglial cells. A total of 109 primary metabolites were detected from heat and freeze-dried samples. Primary metabolite profiling showed higher levels of amino acids (17.4%) and monosaccharides (8.8%) in the heat-dried extracts, whereas high levels of organic acids (64.1%) were present in the freeze-dried samples. The enzymatic activity, such as ATP-citrate synthase, pyruvate kinase, glyceraldehyde-3-phosphatase dehydrogenase, glutamine synthase, fructose-bisphosphate aldolase, and D-3-phosphoglycerate dehydrogenase, related to the reverse tricarboxylic acid cycle were significantly high in the heat-dried samples. We also observed a decreased phosphorylation level of the MAP kinase (Erk1/2, p38, and JNK) and NF-kappa B subunit p65 in the heat-dried samples of the BV2 microglia cells. The current study suggests that heat drying improves the production of ganoderic acids by the upregulation of TCA-related pathways, which, in turn, gives a significant reduction in the inflammatory response of LPS-induced BV2 cells. This may be attributed to the inhibition of NF-kappa B and MAP kinase signaling pathways in cells treated with heat-dried extracts.

Automated summary

The study investigated the effects of different postharvest drying protocols on the metabolites profiling of Ganoderma lucidum, finding higher levels of amino acids and monosaccharides in heat-dried extracts, and high levels of organic acids in freeze-dried samples. Enzymatic activity related to the reverse tricarboxylic acid cycle was significantly high in heat-dried samples, leading to a reduction in the inflammatory response of LPS-induced BV2 cells. Heat drying was shown to improve the production of ganoderic acids by upregulating TCA-related pathways and inhibiting NF-kappa B and MAP kinase signaling pathways.