title: The Effect of Temperature on Pressurised Hot Water Extraction of Pharmacologically Important Metabolites as Analysed by UPLC-qTOF-MS and PCA.
abstract: Metabolite extraction methods have been shown to be a critical consideration for pharmacometabolomics studies and, as such, optimization and development of new extraction methods are crucial. In the current study, an organic solvent-free method, namely, pressurised hot water extraction (PHWE), was used to extract pharmacologically important metabolites from dried Moringa oleifera leaves. Here, the temperature of the extraction solvent (pure water) was altered while keeping other factors constant using a homemade PHWE system. Samples extracted at different temperatures (50, 100, and 150°C) were assayed for antioxidant activities and the effect of the temperature on the extraction process was evaluated. The samples were further analysed by mass spectrometry to elucidate their metabolite compositions. Principal component analysis (PCA) evaluation of the UPLC-MS data showed distinctive differential metabolite patterns. Here, temperature changes during PHWE were shown to affect the levels of metabolites with known pharmacological activities, such as chlorogenic acids and flavonoids. Our overall findings suggest that, if not well optimised, the extraction temperature could compromise the "pharmacological potency" of the extracts. The use of MS in combination with PCA was furthermore shown to be an excellent approach to evaluate the quality and content of pharmacologically important extracts.
authors.affiliation: Department of Biochemistry, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa.
authors.forename: B S
authors.initials: BS
authors.lastname: Khoza
authors.affiliation: Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand (WITS), P/B 3, Johannesburg 2050, South Africa.
authors.forename: L
authors.initials: L
authors.lastname: Chimuka
authors.affiliation: Department of Biochemistry, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa.
authors.forename: E
authors.initials: E
authors.lastname: Mukwevho
authors.affiliation: Department of Biochemistry, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa ; CSIR Biosciences, Natural Products and Agroprocessing Group, Pretoria 0001, South Africa.
authors.forename: P A
authors.initials: PA
authors.lastname: Steenkamp
authors.affiliation: Department of Biochemistry, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa.
authors.forename: N E
authors.initials: NE
authors.lastname: Madala