Extraction Temperatures Shape Water-Soluble Metabolite Profiles of Nepeta nuda L. and thus Modulate the Bioactive Properties.

Background

Plants of the genus Nepeta are widely used in ethnomedicine for treating inflammatory disorders due to their rich content of bioactive compounds. This study investigated how extraction temperature specifically affects the bioactive potential of aqueous extracts from wild-grown Nepeta nuda L.

Methods

The previously used maceration approach for this plant was applied at 30-60 °C to flowers, leaves, and stems. Phytochemical profiling included spectrophotometric assays, metabolite identification, and quantification. Biological activities reported for this plant were assessed, including antioxidant, anti-inflammatory, antiviral, antiproliferative, and antibacterial capacities.

Results

Extraction yield was highest in flowers and leaves, where it increased significantly with rising temperature, while stems were less productive. All plant organs exhibited notable bioactivity falling into two groups: lower temperatures (30 and 40 °C) were optimal for antiviral and anti-inflammatory effects, whereas and higher temperatures (50 and 60 °C) enhanced antioxidant potential. The phytochemical composition, evaluated at representative extraction temperatures, revealed differential accumulation of p-coumaric acid and luteolin in all organs at 40 °C, while extraction at 60 °C corresponded to elevated levels of phenolic compounds. Flower extracts were confirmed to have the richest metabolic composition and were therefore subjected to further investigation. Extracts obtained at 40 °C influenced C1q binding, supporting their anti-inflammatory activity, whereas extraction at 60 °C resulted in stronger antiproliferative activity in colon cancer cell line. Antibacterial effects were similar at both temperatures.

Conclusions

These findings highlight the importance of optimizing extraction conditions for future pharmacological applications of N. nuda.