Seasonal Changes in the Metabolic Profiles and Biological Activity in Leaves of Diospyros digyna and D. rekoi "Zapote" Trees.

Enrique Ramírez-Chávez,Axel Tiessen,Norma Martínez-Gallardo,José Ordaz-Ortiz,Eduardo Salcedo-Pérez,Ramón Rodríguez-Macías,Ernesto Ramírez-Briones,Jorge Molina-Torres,John P. Délano-Frier,Julia Zañudo-Hernández

doi:10.3390/plants8110449

Abstract

Leaves of semi-domesticated Diospyros digyna and wild D. rekoi trees, sampled seasonally in Mexico in 2014, were analyzed. Metabolic fingerprints revealed higher metabolite diversity in D. rekoi leaves. The TLC bands characteristic of glycosylated flavonoids, predominant in this species, matched the detection of quercetin and quercetin 3-O-glucuronides by liquid chromatography (UPLC-MS) of spring leaf extracts (LEs). Further gas chromatography (GC-MS) analysis revealed abundant fatty acids, organic acids, and secondary metabolites including trigonelline, p-coumaric, and ferulic and nicotinic acids. Phenolic-like compounds prevailed in D. digyna LEs, while unidentified triterpenoids and dihydroxylated coumarins were detected by UPLC-MS and GC-MS. A paucity of leaf metabolites in leaves of this species, compared to D. rekoi, was evident. Higher antioxidant capacity (AOC) was detected in D. digyna LEs. The AOC was season-independent in D. digyna but not in D. rekoi. The AOC in both species was concentrated in distinct TLC single bands, although seasonal variation in band intensity was observed among trees sampled. The AOC in D. digyna LEs could be ascribed to the coumarin esculetin. The LEs moderately inhibited phytopathogenic bacteria but not fungi. Leaf chemistry differences in these Mesoamerican Diospyros species substantiated previous variability reported in tree physiology and fruit physical chemistry, postulated to result from domestication and seasonality.

Highlights

The abundant plant diversity characteristic of Mexico represents a potentially rich source of secondary metabolites having bioactive properties
The High performance thin layer chromatography (HP-TLC) metabolic fingerprints generated by leaf extracts (LEs) of two contrasting Diospyros species were clearly different
This study indicated that the antioxidant capacity (AOC) detected in the Diospyros LEs analyzed, varied among species and among individual trees within a single season

Summary

Introduction

The abundant plant diversity characteristic of Mexico represents a potentially rich source of secondary metabolites having bioactive properties. A significant part of indigenous knowledge about their various beneficial effects is believed to have been lost as the Spanish domination gradually consolidated [1,2] The importance of such plants for many of these cultures, based on their quotidian use, either as a source of food, a curative agent, and/or a communication channel with the divine, was, in many cases, profound. This was manifested, for example, in the assignment of town names, many of which reflect the value that certain plants represented for these people. This refers to the abundance of the characteristic “Zapote” (Diospyros spp.) trees, known as “Tlilzapotl” in the Nahuatl language, which is still relevant in certain regional habitats where they still flourish [3]

Methods

Discussion

Conclusion