Optimization of Subcritical Water Extraction Process for Total Phenolics From Guava and Investigation of Its...

This investigation utilized subcritical water extraction (SWE) technology to isolate polyphenolic components from Psidium guajava fruits. Process optimization was achieved using response surface methodology (RSM), yielding optimal parameters: a 2.07-h extraction duration, operating temperature of 203°C, and a solvent-to-material ratio of 41:1 mL/g. These conditions resulted in a maximum total phenol content of 72.17 mg/g, surpassing conventional methods. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was employed to identify 11 distinct polyphenolic constituents. The antioxidant activity of the extracts was assessed using DPPH•(2,2-Diphenyl-1-picrylhydrazyl radical), ABTS•⁺(2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonat), and PTIO•(2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), with IC₅₀ values of 0.168, 0.065, and 2.21 mg/mL, respectively. Additionally, the ferric ion-reducing power was assessed, with absorbance values ranging from 0.191 to 0.339. The extract demonstrated potential hypoglycemic effects, showing α-glucosidase inhibition at 85.64% (IC₅₀ = 1.16 mg/mL) and α-amylase inhibition at 73.12% (IC₅₀ = 18.99 mg/mL). Additionally, it inhibited tyrosinase by up to 70.32% (IC₅₀ = 1.28 mg/mL), suggesting potential skin-whitening properties. Cytotoxicity studies on HepG2 cells revealed significant inhibition of hepatocellular carcinoma cell proliferation. The bioactive compounds triggered programmed cell death and disrupted the cell cycle, particularly at S and G2/M checkpoints, indicating strong anti-proliferative activity against HepG2 cells. These findings suggest that subcritical water extraction technology can significantly enhance the total phenol content of Guava extracts, offering great potential in natural product extraction. Furthermore, the extract demonstrates substantial biological activity, highlighting its application potential in functional food and medicine. PRACTICAL APPLICATION: The extraction of phenolic compounds from Psidium guajava using subcritical water was optimized through factorial design and RSM. This approach demonstrated the practicality of bioactive component extraction in an industrial setting. The biological activity of the subcritical water total phenol extract was thoroughly evaluated. Based on these findings, the extract shows potential for applications as a natural preservative, functional food ingredient, or medicinal component, suggesting its possible versatility in health-related industries.