Hairy Root-Derived Metabolites from Pelargonium graveolens L'Hér.: Phytochemical Insights and Cosmeceutical Properties

In response to the growing demand for sustainably sourced plant bioactives, this study investigates Pelargonium graveolens L'Hér. as a potential source of phenolic compounds through Agrobacterium rhizogenes -mediated hairy root transformation. Sterile leaf explants were inoculated with strains A4 and ATCC15834 to enhance secondary metabolite production, and T-DNA integration was confirmed by PCR amplification of rol B and rol C genes. The transformed roots were evaluated for transformation efficiency, biomass yield, phenolic accumulation, antioxidant activity, and cosmeceutical potential. The A4 strain exhibited significantly higher hairy-root induction (83.33 ± 6.66%) than ATCC15834 (56.66 ± 3.33%). Comparative analysis showed that A4-HR-L6 root line accumulated greater biomass (14.54 ± 0.41 g FW; 1.43 ± 0.07 g DW/30 mL) and higher total phenolics (172.02 ± 3.19 µg GAE/g DW) and flavonoids (48.06 ± 2.84 µg QE/g DW) than ATCC15834-HR-L9 root line (9.67 ± 1.02 g FW; 0.92 ± 0.09 g DW/30 mL; 96.56 ± 1.05 µg GAE/g DW; 43.45 ± 4.29 µg QE/g DW). HPLC-DAD profiling revealed enrichment of sinapic acid (4163.60 ± 47.73 mg/100 g DW), gallic acid (318.99 ± 12.52 mg/100 g DW), and quercetin-glucoside (929.46 ± 89.66 mg/100 g DW) in A4-HR-L6, while ATCC15834-HR-L9 contained higher 4-hydroxybenzoic (474.03 ± 27.84) and vanillic acids (474.17 ± 42.12) and kaempferol (21834.34 ± 631.52). Antioxidant assays confirmed superior activity for A4 extracts with lower IC₅₀ in DPPH (112.85 ± 7.53 µg/mL) and ABTS (33.79 ± 4.05 µg/mL) tests and higher TAC (133.41 ± 4.53 mg AAE/g DW). Elevated SOD (1.056 ± 0.031 mM/min/mg FW) and POD (7.56 ± 0.43 mM/min/mg FW) activities were also recorded. Cosmeceutical evaluation showed strong inhibition of tyrosinase (IC₅₀ = 64.15 ± 5.91 µg/mL) and elastase (IC₅₀ = 97.84 ± 6.35 µg/mL), with SPF = 10.20 ± 0.61 (90.19% UVB blocking). Correlation analysis linked antioxidant and enzyme inhibition parameters with phenolic accumulation (r = –0.40 to –0.80) and enzymatic activity (r ≥ 0.90). Collectively, these findings demonstrate that A4-mediated transformation markedly enhances phenolic biosynthesis, antioxidant defenses, and cosmeceutical potential in P. graveolens hairy roots.