Nutrient Deficiency-Induced Stress Improves Skincare Effects and Phytochemical Content of Green Extracts from Lamiaceae In Vitro Cultures

The objective of this study was to investigate the impact of nutrient starvation on the growth, biochemical, metabolomic, and biological traits of Lavandula viridis L’Hér and Thymus lotocephalus G. López and R. Morales in vitro cultures. In both species, a reduction in shoot growth and in the production of chlorophyll and carotenoids was observed in cultures grown under nutrient-deficient media (especially Fe and N) compared to those grown under control conditions. The highest levels of hydrogen peroxide and lipid peroxidation, two indicators of oxidative stress, were observed in L. viridis cultures grown under N deficiency and in T. lotocephalus under P and Fe limitation. The results demonstrated that nutrient deficiency led to a 72% and 62% increase in the quantified phenolic compounds in L. viridis and T. lotocephalus, respectively. The highest concentrations of the major compound in both species—rosmarinic acid—were observed in cultures grown under Mg-deficient (60.7 ± 1.0 mg/gDW) and Fe-deficient (50.0 ± 0.4 mg/gDW) conditions in L. viridis and T. lotocephalus, respectively. Furthermore, nutrient starvation enhanced the capacity of green extracts to inhibit three enzymes (tyrosinase, elastase, and hyaluronidase) associated with anti-aging and their antioxidant properties.