Effect of UV-B Radiation on Flavonoids and Phenols Accumulation in Tempisque (Sideroxylon capiri Pittier) Callus.

Karina E Martínez-Silvestre,Nancy Ruiz-Lau,María Celina Luján-Hidalgo,Federico A Gutiérrez-Miceli,Yazmin Sánchez-Roque,José Alfredo Santiz-Gómez

doi:10.3390/plants11040473

Abstract

Tempisque (Sideroxylon capiri Pittier) is classified as a threatened species and has been reported with a high content of phenols and flavonoids in the leaves. The use of abiotic elicitors such as radiation has been reported due to the changes it produces in the metabolism of plants by activating their defense mechanisms and increasing the biosynthesis of bioactive compounds with antioxidant capacity such as phenols and flavonoids. Therefore, the aim of this work was to evaluate the effect of UV-B radiation on growth parameters and the synthesis of bioactive compounds in in vitro culture of tempisque callus. For the callus induction, we used thidiazuron (TDZ) and 2,4-dichlorophenoxyacetic acid (2,4-D) at 0, 0.5 and 1 mg/L. Calluses were exposed to UV-B radiation (0, 1, 2, 3 and 4 h/day) for two and four weeks. The highest callus formation index was obtained with TDZ and 2,4-D at 1 mg/mL. The greatest increase in the concentration of phenols and flavonoids was detected in the fourth week with 4 h of exposure per day. The highest concentrations of quercetin (230 µg/g dry weight), kaempferol (235 µg/g dry weight) and gallic acid (240 µg/g dry weight) were found in callus obtained from leaves explants.

Highlights

The tempisque (Sideroxylon capiri Pittier) is a timber tree that grows up to 40 m high, and it is distributed from Mexico to Panama [1]
With respect to the callus formation index (CFI), it is observed that when plant growth regulators are used individually, the callus formation index is low compared to when 2,4-D
Induced less-compact, spongy, and in some cases friable calluses in calluses obtained from both leaf and stem explants, TDZ induced calluses with less phenolization compared to the treatments where only 2,4-D was used (Figure 2), so these results show that the use of TDZ is crucial in the induction of callogenesis in tempisque

Summary

Introduction

The tempisque (Sideroxylon capiri Pittier) is a timber tree that grows up to 40 m high, and it is distributed from Mexico to Panama [1]. The tempisque is a tree whose leaves and fruits are edible and are used as a condiment in food and for some kidney diseases and it has been qualitatively determined that the leaf extracts contain secondary metabolites such as phenols and flavonoids mainly, but steroids and tannins have been determined [4]. This species could be a good source of secondary metabolites with important properties for the pharmaceutical and food industry due to the leaf extracts being practically non cytotoxic, so their use could be safer in relation to the absence of saponins and alkaloids since toxic properties have been attributed to these compounds [4]. Leaf extract of tempisque has allowed potassium nanoparticle synthesis due to the secondary metabolites it contains, and these phytonanoparticles have shown effectiveness versus pathogenic microorganisms such as Bacillus cereus, Enterobacter aerogenes, Fusarium solani and Botrytis cinerea [5]

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