Plant extracts have potential as food additives. In this sense, this work aimed to study the bioactivities of plant extracts and their ability as health-promoting additives.

Lavender, lemon balm, basil, tarragon, sage, and spearmint dry aerial parts were mechanically ground. Three extraction methods were tested: infusion and decoction, using distilled water as solvent and a sample/solvent ratio of 1:100; and hydroethanolic extraction, using ethanol 80% (v/v) as solvent and a sample/solvent ratio of 1:60.

The extracts obtained were evaluated for their antimicrobial and antifungal activities, by a microdilution method. The antioxidant activity was evaluated through the lipid peroxidation inhibition assay (TBARS) and the oxidative haemolysis inhibition assay (OxHLIA). Cytotoxic activity was evaluated in tumour and non-tumour cell lines using the sulforhodamine B method, and anti-inflammatory activity in lipopolysaccharide-activated RAW 264.7 macrophages by the ability to inhibit NO production.

The results showed that all extracts exhibited antimicrobial activity against six pathogens tested (MIC ≤ 2 mg/mL) and antifungal capacity against, at least, five fungi (MFC ≤ 1 mg/mL).

In the TBARS evaluation, lemon balm infusion (125±2 μg/mL) and hydroethanolic extracts of spearmint (132±5 μg/mL) and lavender (177±4 μg/mL) presented the highest activities. In the OxHLIA assay, sage decoction (8.9±0.4 μg/mL) and hydroethanolic extracts of spearmint (12.5±0.2 μg/mL) and lemon balm (13.5±0.4 μg/mL) showed the best capacities to inhibit oxidative haemolysis.

Regarding the anti-inflammatory activity, only the extracts of spearmint and basil, and the decoction and hydroethanolic extracts of tarragon, showed promising results (GI₅₀<89 μg/mL). As for the cytotoxicity assay, most extracts (except those of tarragon and the infusion and decoction of basil) revealed anti-proliferative capacity in the AGS, CaCo, and HeLa tumour lines (GI₅₀<400 μg/mL).

These outcomes provide insight on the bioactivity of numerous herbal extracts, emphasising their value as food additives to prevent spoilage and deliver beneficial health effects.