Abstract
Extraction plays a vital role in the study of phytochemicals as the quality of analytical results have often been directly linked to the efficacy of the extraction process. Conventional methods of phytochemical extraction utilize large quantities of organic solvents which stirs issues of safety and environmental health. Moreover, these methods are often labourious, time consuming and expensive. It was therefore imperative to look for an alternative method of phytochemical extraction that is efficient, cost-effective and more eco-friendly. Pressurized hot water extraction (PHWE) which is often referred to as subcritical water extraction (SWE) has promising prospects, and when properly harnessed (optimized) often deliver results that compare favourably to conventional methods. This current research work considered the application of PHWE together with front-line chromatographic and mass spectrometric analytical techniques, i.e. ultra-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometry (UPLC-qToF-MS/MS) and multivariate chemometric analysis for investigating the phytochemical (flavonoids and di-acylated cinnamic acids) profile of Bidens pilosa, an indigenous and very potent medicinal plant.
The first phase of the study considered the extraction of flavonoid compounds from B. pilosa using PHWE at temperatures of 50, 100 and 150ᵒC and subsequent analysis on UPLC-qToF-MS/MS. The findings revealed the possibility of extracting and characterizing 28 different molecules belonging to different classes of flavonoids i.e. chalcones, flavonols and flavanones. These molecules have been reported to perform various important biological activities such as being anti-oxidative, hepatoprotective, anti-cancer and antibacterial properties. Further analysis of the data using chemometric principal component analysis (PCA) showed that the different temperatures studied yielded significantly different recovery patterns for the identified molecules. Generally, higher temperatures resulted in better extraction yields, as such, extracts obtained at 150ᵒC resulted in the highest yields of the identified flavonoids.
In a subsequent experiment, PHWE was optimized using a cosolvent (methanol) for the extraction of di-acylated cinnamic acids, specifically, dicaffeoylquinic acid (diCQA) and chicoric acid (CA) and their analogues, because it is common observation that these metabolites (particularly CA) are highly unstable during extraction and degrade at elevated temperatures. Further to this is the fact...
M.Tech. (Food Technology)