Metabolite variations and antioxidant activity of Muntingia calabura leaves in response to different drying methods and ethanol ratios elucidated by NMR‐based metabolomics

• Published in: Phytochemical analysis 2021-01, Vol.32 (1), p.69-83
• Main Authors: Zolkeflee, Nur Khaleeda Zulaikha, Isamail, Nor Amira, Maulidiani, Maulidiani, Abdul Hamid, Nur Ashikin, Ramli, Nurul Shazini, Azlan, Azrina, Abas, Faridah
• Format: Article
• Language: English
• Subjects: 1H‐NMR metabolomics; Amino acids; Antioxidants; Bioactive compounds; Biological activity; Correlation analysis; DPPH scavenging activity; Drying; Drying ovens; Ethanol; Leaves; Magnetic Resonance Spectroscopy; Metabolites; Metabolomics; Muntingia calabura; Nitric oxide; nitric oxide scavenging; NMR; Nuclear magnetic resonance; Organic acids; Phenolic compounds; Phenols; Phytosterols; Plant extracts; Plant Extracts - pharmacology; Plant Leaves; Principal components analysis; Scavenging; Sugar; TPC assay; Variation
• ISSN: 0958-0344; 1099-1565
• DOI: 10.1002/pca.2917

Introduction Muntingia calabura from the Muntingiaceae family has been documented for several medicinal uses. The combinations of drying treatment and extracting solvents for a plant species need to be determined and optimised to ensure that the extracts contain adequate amounts of the bioactive metabolites. Objective Evaluate the metabolite variations and antioxidant activity among M. calabura leaves subjected to different drying methods and extracted with different ethanol ratios using proton nuclear magnetic resonance (1H‐NMR)‐based metabolomics. Methodology The antioxidant activity of M. calabura leaves dried with three different drying methods and extracted with three different ethanol ratios was determined by using 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and nitric oxide (NO) scavenging assays. The metabolites variation among the extracts and correlation with antioxidant activity were analysed by 1H‐NMR‐based metabolomics. Results Muntingia calabura leaves extracted with 50% and 100% ethanol from air‐drying and freeze‐drying methods had the highest total phenolic content and the lowest IC50 value for the DPPH scavenging activity. Meanwhile, oven‐dried leaves extracted with 100% ethanol had the lowest IC50 value for the NO scavenging activity. A total of 43 metabolites, including sugars, organic acids, amino acids, phytosterols, phenolics and terpene glycoside were tentatively identified. A noticeable discrimination was observed in the different ethanol ratios by the principal component analysis. The partial least‐squares analysis suggested that 32 compounds out of 43 compounds identified were the contributors to the bioactivities. Conclusion The results established set the preliminary steps towards developing this plant into a high value product for phytomedicinal preparations. Muntingia calabura is widely cultivated in southeast Asia. The present study aims to evaluate the metabolite variations among M. calabura leaves extracts and correlation with its antioxidant activity using 1H‐NMR‐based metabolomics. The 50% and 100% ethanolic extracts from air‐drying and freeze‐drying methods shows the best total phenolic content value and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) scavenging activity, while 100% ethanolic extract from oven‐drying method shows the best nitric oxide (NO) scavenging activity. Sugars, organic acids, amino acids, phytosterols, phenolics and terpene glycoside were among the potential antioxidant contributors.