Epimeric Mixtures of Brassinosteroid Analogs: Synthesis, Plant Growth, and Germination Effects in Tomato (Lycopersicum esculentum Mill.)

Nitza Soto,Yamilet Coll,Andrés F Olea,Katy Díaz,Luis Espinoza,César González,Marco Mellado

doi:10.3390/agronomy10060808

Abstract

Brassinosteroids (BRs) play an important role in the growth and development of plants. Herein, we describe the synthesis of epimeric mixtures of BR analogs with 24-norcholane type side chains, S/R configuration at C22 and A/B ring cis-type fusion. All epimeric mixtures were synthetized from hyodeoxycholic acid. The biological activity of mixtures was evaluated by using rice lamina inclination test and germination of tomato (Lycopersicum esculentum) seeds. The results show that these epimeric mixtures exhibit similar bioactivity to brassinolide in both bioassays. Thus, our results corroborate that the A/B junction has almost no effect on bioactivity and open the possibility of using epimeric mixtures instead of pure compounds. In this approach, the synthesized BR analogs maintain a good level of bioactivity, whereas the synthesis is shorter, cheaper and with higher yields. All these factors make this alternative very interesting for potential application.

Highlights

Brassinosteroids (BRs) are plant polyhydroxysteroids that from the pivotal discovery of brassinolide (BL) by Grove et al [1] and have been found all around the plant kingdom [2,3].BRs participate in a series of physiological, biochemical and response processes in plants, such as cell division and elongation, photomorphogenesis, flower developmental processes, male sterility, stomatal developmental processes and enzyme activation [4–9]
Both formyl functions in compound 2 was confirmed by 1 H-NMR
Our results suggest that the presence of hydroxyl groups in the mixtures

Summary

Introduction

BRs participate in a series of physiological, biochemical and response processes in plants, such as cell division and elongation, photomorphogenesis, flower developmental processes, male sterility, stomatal developmental processes and enzyme activation [4–9]. BRs are naturally found in seeds and it has been shown that they play an important role in promotion of seed germination [10]. It was observed that the percentage of germination in Cicer arietinum, Triticum aestivum and Brassica juncea, was increased by soaking seeds in BR solutions [11–14]. The applied research on BRs has been done mainly in agriculture [5]; there have been some studies in forestry showing that. BRs stimulate seed germination of forest species such as Robinia pseudoacacia L, Pinus tabulaeformis. Rapid and synchronized germination is an important feature in commercial plant production in both agriculture and forestry.

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