Pressurized hot water extraction (PHWE) has been classified as a green extraction technology, which is used for the extraction of bioactive compounds from plants. However, very few optimization strategies for the efficient extraction of bioactive compounds have been done. In the current study, optimization of PHWE of flavonoids from Momordica foetida was attempted with the aid of ultra-performance liquid chromatography-quadrupole time of flight mass spectrometry (UHPLC-qTOF-MS) and multivariate chemometric models. Plant metabolite extraction was achieved by altering the extraction temperature (100-300°C) during PHWE. UHPLCqTOF-MS analysis of the extracts revealed temperatures between 150 and 250°C to be optimal for the extraction of flavonoid molecules. Furthermore, analysis of the data using multivariate models such as principal component analysis (PCA) revealed various flavonoid distribution patterns between extracts obtained using these various temperatures. In addition, isomeric flavonoids with similar structural core conformations were also seen to be differentially extracted at the various temperatures. The use of UHPLC-MS and highdimensional chemometric models allowed for comprehensive optimization of the PHWE. The use of MS in combination with PCA is an excellent approach to evaluate the quality and content of pharmacologically relevant metabolites from subcritical fluid plant extracts.

Host-pathogen interactions in plants are complex and potentially influenced by heat shock/stress (HS). Host HS proteins (HSPs) induced prior to bacterial exposure may facilitate the folding of newly synthesized defense proteins and promote incompatible host-pathogen interactions. We hypothesized that a non-lethal HS, with recovery, promotes protection of Nicotiana tabacum during subsequent exposure to avirulent soilborne necrotrophic pathogen Ralstonia solanacearum. The objective of this study included investigating the effects of HS with or without recovery on the outcome of bacterial exposure to a virulent and avirulent biovar of R. solanacearum in N. tabacum cell suspensions. This was assessed by quantifying host Hsp70/Hsc70 levels, mitochondrial electron (e − ) transport activity as a marker of viability, and phosphatidylserine externalization and DNA fragmentation as markers of apoptosis. Our findings support the hypothesis that HS, with recovery, promotes protection of N. tabacum during subsequent exposure to R. solanacearum, suggesting a role for Hsp70/Hsc70 in the observed protection of e − transport, increased apoptosis, and DNA fragmentation.