Unravelling the Photoprotection Properties of Garden Cress Sprout Extract

Abstract

Plants, as with humans, require photoprotection against the potentially damaging effects of overexposure to ultraviolet (UV) radiation. Previously, sinapoyl malate (SM) was identified as the photoprotective agent in thale cress. Here, we seek to identify the photoprotective agent in a similar plant, garden cress, which is currently used in the skincare product Detoxophane nc. To achieve this, we explore the photodynamics of both the garden cress sprout extract and Detoxophane nc with femtosecond transient electronic absorption spectroscopy. With the assistance of liquid chromatography-mass spectrometry, we determine that the main UV-absorbing compound in garden cress sprout extract is SM. Importantly, our studies reveal that the photoprotection properties of the SM in the garden cress sprout extract present in Detoxophane nc are not compromised by the formulation environment. The result suggests that Detoxophane nc containing the garden cress sprout extract may offer additional photoprotection to the end user in the form of a UV filter booster.

Keywords: UV filter; nature-inspired; photochemistry; photodynamics; photophysics; photoprotection; plant sunscreen; sinapoyl malate; sunscreen; ultrafast spectroscopy.

Figure 1

(A) Molecular structure of trans-sinapoyl malate. UV–Vis spectra of samples obtained for (B) 0.01 mg/mL trans-sinapoyl malate in water (red), 0.1 mg/mL of garden cress sprout extract in water (green), and (C) Detoxophane nc diluted at a ratio of 1:100 in water.

Figure 2

(A) UHPLC analysis of the garden cress sprout extract, highlighting compounds eluting at between 10 and 20 min and absorbing in the 210–390 nm range. (B) Extracted ion chromatogram of cress sprout (green) and sinapoyl malate standard (red) for m/z values calculated for [SM+H]⁺, SM ammonium adduct, and SM sodium adduct (C) Mass spectra for cress sprout and sinapoyl malate at retention time of 15.9 min.

Figure 3

TEA spectra obtained for 0.1 g of cress sprout extract in 25 mL of (A) dioxane and (B) water, photoexcited at 330 nm, with spectra presented as false colour maps. The same data are presented as line plots of mΔOD vs. probe wavelength at selected pump–probe delay times in (C,D) for cress sprout extract in dioxane and water, respectively. (E,F) The evolution associated difference spectrum (EADS) for cress sprout extract in dioxane and water, respectively, produced by the fitting procedure. The inset (E,F) shows the transient absorption spectrum at the maximum available pump–probe delay of 2 ns.

Figure 4

TEA spectra obtained for the bulk solution of Detoxophane nc photoexcited at 330 nm, shown as a false colour map (A). The same data are presented as a line plot of the mΔOD vs. probe wavelength at selected pump–probe delay times in (B). The EADS is shown in (C), with the 2 ns transients presented as an inset.