Effects of Gamma Irradiation on Changes in Chemical Composition and Antioxidant Activity of Euphorbia maculata Callus

Abstract

In this study, we investigated the effects of gamma irradiation on the antioxidant activity and metabolite profiles of Euphorbia maculata calli (PC3012). Gamma irradiation at various doses (0, 0.05, 0.5, and 10 kGy) significantly enhanced the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS⁺) radical scavenging activities of the callus extracts of PC3012 in a dose-dependent manner. High-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography-quadrupole time-of-flight/mass spectrometry (UPLC-Q-TOF/MS) analyses revealed that irradiation increased the lysophospholipid content, although no new antioxidant compounds were formed. Furthermore, a PLS-DA analysis revealed evident metabolic differences between non-irradiated and irradiated samples, which were further verified by statistical validation. These findings suggest that gamma irradiation induces specific biochemical modifications that enhance the bioactive properties of PC3012 calli. This technology exhibits potential for utilization in the natural product and food sectors, particularly in the development of functional foods and nutraceuticals with improved health benefits.

Keywords: Euphorbia maculata; UPLC-QTOF/MS; gamma irradiation; plant-derived callus; radical scavenging.

Figure 1

DPPH and ABTS⁺ radical scavenging activities of three plant-derived calli after gamma irradiation. (A) DPPH radical scavenging assay; (B) ABTS⁺ radical scavenging assay. Radical scavenging ability was measured at 100 μg/mL. The results are expressed as mean ± SD (n = 3). Statistical analyses were performed using a two-way ANOVA, followed by Tukey’s post hoc test. Different letters represent statistically significant differences at p < 0.05. PC0312: E. maculata callus; PC3026: P. granatum callus; PC3062: P. fragarioides callus.

Figure 2

DPPH and ABTS⁺ radical scavenging activities of E. maculata callus extracts at gamma radiation doses of 0, 0.05, 0.5, and 10 kGy. (A) DPPH radical scavenging assay; (B) ABTS⁺ radical scavenging assay. Radical scavenging ability was measured at 100 μg/mL. The results are expressed as mean ± SD (n = 3). Statistical analyses were performed using a two-way ANOVA, followed by Tukey’s post hoc test. Different letters represent statistically significant differences at p < 0.05. PC: (+)-Catechin used as a positive control.

Figure 3

HPLC chromatograms of non-irradiated and irradiated E. maculata (PC3012) callus extracts. (A) 254 nm; (B) 360 nm. See the Materials and Methods section for experimental conditions. Arrow shows the increased peak by gamma irradiation in plant callus.

Figure 4

TIC chromatograms of non-irradiated (A) and irradiated (B) E. maculata calli (PC3012). Refer to the Materials and Methods section for experimental conditions.

Figure 5

Changes in metabolite content (%) of non-irradiated and irradiated Euphorbia maculata calli (PC3012). The results are expressed as the mean ± standard deviation (n = 3). * p < 0.05 vs. the non-irradiated groups. Refer to Metabolite number in Table 1.

Figure 6

PLS-DA scores scatter plot and permutation test analysis of metabolite profiles of non-irradiated and irradiated E. maculata calli (PC3012). △: R2 values, ■: Q2 values.