Fruiting body, spores and in vitro produced mycelium of ganoderma lucidum from northeast Portugal : a comparative study of the antioxidant potential of phenolic and polysaccharidic extracts

Abstract

Ganoderma lucidum is one of the most extensively studied mushrooms due to its medicinal properties. Herein, a systematic study was carried out in order to compare the antioxidant activity of phenolic and polysaccharidic extracts from fruiting body, spores and mycelium, obtained in three different culture media, of G. lucidum from Northeast Portugal. Phenolic extracts were characterized using high-performance liquid chromatography coupled to photodiode array detection, while polysaccharidic extracts were hydrolysed and further characterized using HPLC and refraction index detection. In general, the phenolic extracts (Ph) proved to have higher antioxidant potential than their corresponding polysaccharidic extracts (Ps). Amongst phenolic extracts, FB-Ph provided the highest antioxidant activity (EC50 ≤ 0.6 mg/ml) and the highest content in total phenolics (~29 mg GAE/g extract) and phenolic acids (p-hydroxybenzoic and p-coumaric acids). S-Ps was the polysaccharidic extract with the best antioxidant activity (EC50 ≤ 2 mg/ml); nevertheless, the highest levels of total phenolics were obtained in FB-PS (~56 mg GAE/g extract), while the highest levels of total polysaccharides (~14 mg PE/g extract) and individual sugars were observed in mycelia obtained from solid culture media, M-PDA-Ps and M-sMMN-Ps. The free radical scavenging properties, reducing power and lipid peroxidation inhibition of G. lucidum seemed to be correlated with phenolic compounds mostly in a free form, but also linked to polysaccharides.The authors are grateful to Fundação para a Ciência e a Tecnologia (FCT, Portugal) and COMPETE/QREN/UE (research project PTDC/AGR-ALI/110062/2009) for financial support. S.A. Heleno (BD/70304/2010) and L. Barros (BPD/4609/2008) thank to FCT, POPH-QREN and FSE for their grants. The GIP-USAL is financially supported by the Spanish Ministerio de Ciencia e Innovación through the Consolider-Ingenio 2010 Programme (FUN-C-FOOD, CSD2007-00063), and Junta de Castilla y León (Grupo de Investigación de Excelencia, GR133)