Relationship analysis between flavonoids structure and subcritical water extraction (SWE)

Area of Science:

• Green Chemistry
• Natural Product Chemistry
• Analytical Chemistry

Background:

• Subcritical water extraction (SWE) utilizes water's tunable properties as a solvent.
• Flavonoids are plant compounds with diverse health benefits, often extracted using various methods.

Purpose of the Study:

• To determine optimal subcritical water extraction conditions for flavonoids from eight plant sources.
• To investigate the influence of flavonoid chemical structure on extraction efficiency.

Main Methods:

• Subcritical water extraction (SWE) was performed at varying temperatures and times.
• The polarity of flavonoid side chains, presence of sugar moieties, and double bonds were analyzed for their impact.

Main Results:

• Optimal extraction temperatures varied based on flavonoid structure: OH side chains (e.g., quercetin) extracted at 170°C, O-CH3 and H side chains (e.g., isorhamnetin, kaempferol) at 190°C.
• Glycosides (e.g., quercitrin, spiraeoside) were extracted at lower temperatures (110-150°C) than their aglycones (170-190°C).
• Flavonoids with double bonds (e.g., apigenin) required higher temperatures (190°C) compared to those without (e.g., naringenin at 170°C).

Conclusions:

• Subcritical water extraction is a tunable method for flavonoid isolation.
• Flavonoid chemical structure, including side chain polarity, glycosylation, and unsaturation, dictates optimal extraction conditions.