A Bioactive Emulgel Formulation of Equisetum telmateia Ehrh. Methanol Extract: Integrating Antioxidant Activity, Skin Enzyme Inhibition, and Permeation Kinetics

Abstract

Equisetum telmateia Ehrh. (great horsetail) belongs to the Equisetaceae family and its aerial parts have been traditionally used for skin conditions and to achieve healthy and resilient skin, nails, and hair. This study aimed to evaluate the inhibition of skin-related enzymes by, the antioxidant capacity of, and the phytochemical composition of E. telmateia. Additionally, a novel emulgel was formulated from the main methanolic extract and characterized in terms of pH, viscosity, determination of content quantification, textural profile analysis, and spreadability. After the characterization studies, in vitro release and ex vivo permeation and penetration studies were performed. Firstly, the dried aerial parts of E. telmateia were macerated in methanol, followed by partitioning with solvents of increasing polarity: n-hexane, chloroform, ethyl acetate, and n-butanol. Antioxidant activity was assessed using DPPH, FRAP, CUPRAC, and TOAC assays, while enzyme inhibition was analyzed for collagenase, elastase, hyaluronidase, and tyrosinase. LC-MS/MS analysis identified 53 phytochemical compounds. Protocatechuic acid, the main phenolic compound, was quantitatively analyzed in each subfraction by HPTLC. The in vitro release studies showed sustained release of the reference substance (protocatechuic acid) and the kinetic modeling of the release was fitted to the Higuchi model. The ex vivo permeation and penetration studies showed that the formulation exhibited a retention of 3.06 ± 0.21 µg.cm^-2 after 24 h, whereas the suspended extract demonstrated a skin retention of 1.28 ± 0.47 µg.cm^-2. Both the extracts and the formulated emulgel exhibited inhibitory effects on skin-related enzymes. Our finding suggested that E. telmateia might be a valuable ingredient for wrinkle care and skin-regenerating cosmetics.

Keywords: Equisetum telmateia; HPLC; LC-MS/MS; emulgel; skin-related enzyme inhibition.

Figure 1

LC-MS/MS chromatograms of ETM.

Figure 2

HPTLC analysis of the extracts. (A) UV spectra of protocatechuic acid and same Rf value of tracks at 200–450 nm. (B) HPTLC chromatograms of protocatechuic acid. (C) Example chromatogram of ETE (ethyl acetate extract of ET). (D) 3D HPTLC chromatogram of protocatechuic acid analysis of Equisetum telmateia extracts at 366 nm. (E) HPTLC chromatograms of ETH: hexane fraction of ET, ETC: chloroform fraction of ET, ETE: ethyl acetate fraction of ET, ETB: n-butanol fraction of ET, ETM: methanolic extract of ET, ETW: remaining water fraction of ET. Mobile phase: toluene: ethyl acetate: formic acid (7:5:0.5). Derivatization: NPR reagent. Visualization: 366 nm.

Figure 3

Cumulative in vitro release of protocatechuic acid from ETS and ETF.

Figure 4

Cumulative ex vivo permeation and penetration of protocatechuic acid of ETS and ETF.

Figure 5

Skin-related enzyme inhibitory effect of ET, novel formulation, and all fractions. Different letters indicate significance (p < 0.05). Inhibitory effects of ETM (methanolic extract of ET 1 mg/1 mL), ETH (hexane fraction of ET 1 mg/1 mL), ETC (chloroform fraction of ET 1 mg/1 mL), ETE (ethyl acetate fraction of ET 1 mg/1 mL), ETB (n-butanol fraction of ET 1 mg/1 mL), ETW (remaining water fraction of ET1 mg/1 mL), ETF (emulgel formulation of ET) on collagenase (A), elastase (B), hyaluronidase (C), tyrosinase (D). Standards: EGCG: epigalloctechin gallate (1 mg/mL for anticollagenase activity, 0.25 mg/mL for antielastase activity), TA: tannic acid (1.1 mg/mL), KA: kojic acid (1 mg/1 mL).