*3.4. Lipid Metabolism Affected by the Post-Harvest Jasmonate Treatment*

The metabolite profiling of the tomato fruit pericarp treated only with 1-methylcyclopropene and with both 1-methylcyclopropene and methyl jasmonate showed a significant impact on the fruit quality and, consequently, the ripening process. Although the profiles of sugars, organic acids, and amino acids were affected by the jasmonate treatment, the most remarkable difference observed was in the lipid metabolism.

Fruits treated with methyl jasmonate showed a positive impact on the accumulation of metabolites, mainly in the non-polar metabolites (fatty acids, carotenoids, tocopherols, and phytosterols). The application of exogenous methyl jasmonate in fruits with blocked ethylene receptors showed that methyl jasmonate could act independently of endogenous ethylene, suggesting that the blocking of ethylene receptors was reversed after 10 DAH, or new ethylene receptors were synthesized. Post-harvest treatment with jasmonate showed that it is possible to obtain an improved fruit quality with a prolonged shelf life.

Oleic, capric, lauric, palmitic, stearic, and myristic acids showed a 17-fold reduction when treated with only 1-methylcyclopropene and up to an 11-fold reduction when treated with both methyl jasmonate and 1-methylcyclopropene, as compared to the untreated fruits at 10 DAH. It is noteworthy that a drastic decrease was observed in the levels of linoleic and myristic acids at 4 DAH with both treatments (Table 1, Figure 2). Additionally, reductions in the levels of carotenoids, tocopherols, and phytosterols were also detected at the onset of ripening (Figure 6, Tables S1 and S2).

Conversely, an interesting increase in the levels of lignoceric, cerotic, and α-linolenic acids at 4 DAH and palmitic and linoleic acids at 21 DAH with both treatments was detected (Figures 2 and 5). Moreover, notable accumulations in the levels of secondary metabolites, such as lycopene, β-carotene, lutein, α-, β-, and γ-tocopherols, β-sitosterol, stigmasterol, and stigmastadienol, were detected at 21 DAH by the action of methyl jasmonate (Figure 6, Tables S1 and S2). However, it is noteworthy that the maturation stage and hormonal regulation may not be the only factors responsible for the improved lipid metabolism in tomato fruits; other factors such as genetic factors, cultural practices, cultivation, and environmental conditions should be considered [25]. Understanding the interactions between hormone treatment and environmental factors, genotype, and agronomic practices is essential to produce high-quality fruits by improving the synthesis of high-value nutrients.

The treatment with methyl jasmonate can induce significant changes in the metabolite profile of tomato fruits during ripening, positively impacting the nutritional and sensory fruit quality. This treatment, associated with the blocking of ethylene receptors with 1 methylcyclopropene, proved effective in avoiding potential effects on the post-harvest life of the fruits due to the increase in ethylene synthesis caused by methyl jasmonate. Our experimental design involved four replicates, and the consistency of the results indicates that the effects have good reproducibility. However, they were conducted only on the Grape cultivar, and it would be interesting to reproduce these treatments in other cultivars to assess the influence of genotype on responses to treatment with methyl jasmonate and 1-methylcyclopropene. From the viewpoint of applicability, the presented protocol has good commercial potential, since the concentrations of methyl jasmonate and 1-methylcyclopropene used were low and, consequently, did not require large volumes of the compounds. The volatility of the compounds and simplicity of the method of exposure of the fruits make the treatments feasible for larger environments, such as commercial chambers. Although both substances are considered generally recognized as safe (GRAS), further studies about the impact on sensory quality would be important to assess consumer acceptability for the treated fruit.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10 .3390/foods10040877/s1, Table S1: Carotenoids contents (μg.g−<sup>1</sup> FW) in tomato pericarp (*Solanum lycopersicum* L. cv. Grape) exposed to 1-methylcyclopropene (MCP) and both 1-methylcyclopropene and methyl jasmonate (MCP+ MeJA) treatments at 04, 10, and 21 days after harvest (DAH), detected by high performance liquid chromatography (HPLC); Table S2: Tocopherols, phytol, and phytosterols in tomato pericarp (*Solanum lycopersicum* L. cv. Grape) exposed to 1-methylcyclopropene (MCP) and both 1-methylcyclopropene and methyl jasmonate (MCP+ MeJA) treatments at 04, 10, and 21 days after harvest (DAH), detected by gas chromatography-mass spectrometry (GC-MS).

**Author Contributions:** Investigation, Writing and original draft preparation: S.L.R.M.; Writing review and editing: I.L.M., and E.d.C.T.; methodology, software: G.B.P.; data curation: I.L.M.; supervision: E.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the São Paulo Research Foundation (FAPESP, Grant 2013/07914-8) and Coordination for the Improvement of Higher Education Personnel (CAPES, Grant 88882.376974/2018- 01).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** https://repositorio.uspdigital.usp.br/ accessed on 15 April 2021.

**Acknowledgments:** The authors gratefully acknowledge the financial support of the São Paulo Research Foundation (FAPESP, Grant 2013/07914-8), Coordination for the Improvement of Higher Education Personnel (CAPES, Grant 88882.376974/2018-01), and the National Council for Scientific and Technological Development (CNPq, Grant 312605/2019-6). The authors also thank T. M. Shiga, A. de Oliveira, L. F. L. Macedo, and L. H. J. da Silva for the technical assistance.

**Conflicts of Interest:** The authors declare no conflict of interest.
