Hindawi Journal of Food Quality Volume 2021, Article ID 6620446, 6 pages https://doi.org/10.1155/2021/6620446 Research Article Polyphenol Content and Antioxidant Activity of Stevia and Peppermint as a Result of Organic and Conventional Fertilization Lina Garcia-Mier,1 Adriana E. Meneses-Reyes,2 Sandra N. Jimenez-Garcia,3 Adan Mercado Luna,2 Juan Fernando Garcı´a Trejo,2 Luis M. Contreras-Medina,2 and Ana A. Feregrino-Perez 2 1Divisio´n de Ciencias de la Salud, Universidad del Valle de Me´xico, Campus Quere´taro. Blvd. Juriquilla No. 1000, Santa Rosa J´auregui, C.P. 76230, Santiago de Quer´etaro, Qro, Mexico 2Facultad de Ingenier´ıa, Universidad Auto´noma de Quere´taro, C.U. Cerro de las Campanas S/N, Colonia Las Campanas, C.P. 76010, Santiago de Quere´taro, Quere´taro, Mexico 3Departamento de Enfermer´ıa y Obstetricia, Divisi´on de Ciencias de la Salud e Ingenier´ıa, Campus Celaya-Salvatierra, Universidad de Guanajuato, Av. Mutualismo Esq. Prolongacio´n R´ıo Lerma S/N, Celaya, Guanajuato, C.P. 38060, Mexico Correspondence should be addressed to Ana A. Feregrino-Perez; [email protected] Received 26 November 2020; Revised 16 January 2021; Accepted 20 January 2021; Published 31 January 2021 Academic Editor: Giorgia Liguori Copyright © 2021 Lina Garcia-Mier et al. +is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Stevia rebaudiana Bertoni and Mentha piperita are plants that generate interest mainly due to the presence of bioactive compounds in their leaves, such as phenolics. Studies indicate that phenolics have pharmacological and therapeutic properties, including antioxidant activity. Phenolic compounds may be affected by the type of fertilization. For this reason, organic and chemical fertilization were evaluated along with antioxidant activity. Results showed significant differences for total phenols in organic peppermint (62% higher content). Also, DPPH test displayed differences for peppermint and stevia (572% and 16% greater in organic). Organic fertilization may be alternative for producing high added agricultural and commercial products. 1. Introduction sweeteners has emerged due to the increasing health con- sciousness and concern related to sugar consumption and Dietetics products and natural food ingredient demand has the problems related to the safety of some artificial non- increased over the last years. A lot of interest has emerged on nutritive sweeteners [3]. Stevia is an herb of Asteraceae sources of natural antioxidant since many health problems family, which grows wild in South America, such as Para- are associated with the action of toxic forms of oxygen guay and Brazil. Leaves are the economic part of the plant responsible for oxidation processes. Antioxidants are ca- with a high concentration of steviol glycosides [4]. Stevia pable of inhibiting reactive oxygen species (ROS) [1]. rebaudiana Bertoni has been used as a natural sweeter; it is Phenolic compounds may represent approximately 19–23% categorized by high concentration of steviol glycosides in its of dry peppermint leave weight [2]. It has been reported that leaves, which are up to 200 to 400 times sweeter than sucrose. phenolics show beneficial health effects due to free radical In addition to their sweeteners, stevia plants possess other scavenging properties. Mexican population consumes in- compounds such as terpenes, sterols, volatile acids, vitamins, fusions in a regular manner, and one of the most popular is carotenes, organic acids, polysaccharides, hormones, mi- prepared from peppermint (Mentha piperita). Peppermint croelements, and phenolic compounds (tannins and flavo- leaves contain a wide array of bioactive components (fatty noids) [5]. acids, volatile compounds, carotenoids, and phenolic Particularly important for the antioxidant capacity in compounds). At the same time, an interest in natural stevia and peppermint are phenolic compounds, which are 2 Journal of Food Quality secondary metabolites. +e promotion of product quality microplate reader (Multiskan Go model 51119300; +ermo regarding secondary metabolites content may be of high Scientific, Vantaa, Finland) using (+)-catechin (up to relevance for a commercial expansion of stevia and pep- 0.1 mg·mL−1) as a reference standard. A blank sample was permint. Phenolic compounds are involved in various plant prepared by subjecting the original extract to the same processes such as growth and reproduction and are also conditions of reaction without the vanillin reagent. synthesized as a defense mechanism to various stresses; therefore, their production can be enhanced by different 2.4. Quantification of Flavonoids. Briefly, the method for the conditions, among them, type of fertilization. Nowadays, determination of flavonoids content was performed consumers are more concerned of possible exposure to according to Garcia-Mier, Jimenez-Garcia [8]. It consisted agrochemicals. Organic agricultural practices do not allow of mixing 50 μl of the methanolic extract with 180 μl of the use of chemical compounds for crop nutrition, synthetic distilled water and 20 μl of a solution 2-amino- compounds for pest, disease, and weed control. Many have ethyldiphenylborate 1% in a 96-well plate. +e absorbance of suggested that the use of organic fertilizers is an essential the solution was monitored at 404 nm with a microplate source of nutrients for sustainable agriculture and in ad- reader (Multiskan Go model 51119300; +ermo Scientific, dition to cover the physiological requirements of crops, Vantaa, Finland). A rutin standard was prepared in meth- favoring the development of high-quality crops [6]. Due to a anol. Extract absorption was compared with that of a rutin plethora of implications, among them, health benefits and − standard curve (up to 2 μg·ml 1). Flavonoid content was the use of environmental friendly agriculture practices [7], expressed as mg of rutin equivalent per gram of dry sample. the aim of this study was investigating the effect of organic and chemical (conventional) fertilization on the content of bioactive compounds in S. rebaudiana and M. piperita. +e 2.5.QuantificationofTotalPhenols. Total phenols (expressed work is focused on the analysis of antioxidant capacity, as mg of gallic acid equivalent per gram of dry sample) were phenolic compounds, and steviosides levels in those mate- determined by the Folin-Ciocalteu method with modifica- rials, to assess differences between both types of fertilization. tions. To 40 μL of extract were added 460 μL of distilled water, 250 μL of Folin Ciocalteau reagent, and 1250 μL of 2. Materials and Methods 20% sodium carbonate solution. After 2 hours in the dark, samples were read at 750 nm in a UV/Vis spectrophotometer 2.1. Plant Material. Conventional peppermint and stevia (Genesys 10S UV-Vis, +emo Fischer Scientific, USA). plants were obtained from a local supplier. +e plants Gallic acid was used for the calibration curve [9]. belonged to the same batch. Organic stevia plants were got from a commercial greenhouse with organic care located at San Jose´ Iturbide, Guanajuato, Mexico.´ Organic peppermint 2.6. Antioxidant Activity by 1,1-Diphenyl-2-picrylhydrazyl was grown at the Universidad Autonoma´ de Queretaro,´ Radical (DPPH) Inhibition Assay. Radical scavenging Amazcala campus. Leaves were collected and dried at 45°C activity (RSA) was determined using stable radical DPPH for 24 h (Fisher Scientific, 650D, USA). Next, they were method. +e assay was performed following the next milled in a grinder (Krups GX4100, Mexico).´ procedure. All reactions were conducted in 96-well microplates. Aliquot (20 µL) of methanolic extracts was mixed with 100 µM of DPPH (200 µl) in methanol. It was 2.2. Extract Preparation. Extraction for phenolics and an- used a control and a blank. After 30-minute incubation at tioxidant determinations were performed by placing 1 g ambient temperature in darkness, absorbance was recorded (PRACTUM 224-1S; Sartorius, Gottingen,¨ Germany) of at 515 nm in a microplate reader (Multiskan Go model fresh sample in a 50 mL tube and mixed with 10 ml of 51119300; +ermo Scientific, Vantaa, Finland). It was pre- methanol. +e tubes were protected from light and shaken at pared as a calibration curve with Trolox. +e antioxidant 200 rpm (Orbit 1000 model S2030-1000; Labnet, Wood- activity was expressed as percent of inhibition [8]. bridge, NJ, USA) for 24 h at 25°C. After incubation, the samples were centrifuged (Sorvall Biofuge Primo R model 2.7. Antioxidant Activity by 2,2′-Azino-bis(3-ethyl- 75005448; +ermo Scientific, Osterode, Germany) at benzothiazoline-6-sulphonic Acid) (ABTS) Inhibition Assay. 6; 793 × g for 10 min. Aliquots of the supernatant were taken +e radical cation was prepared by mixing 7 mM ABTS stock for the assays. We followed the methods of Garcia-Mier, solution with 140 mM potassium persulfate (1/1, v/v) and Jimenez-Garcia [8]. leaving the mixture for 12 h until reaction was completed and the absorbance was stable. +e ABTS+ solution was 2.3. Quantification of Condensed Tannins. Condensed tan- diluted with ethanol to an absorbance of 0.700 ± 0.05 nm at nins expressed as milligrams of (+)-catechin equivalents per 730 nm for measurement. +e photometric assay was con- gram of dry sample were quantified according to the next ducted on 0.9 mL of ABTS solution and 0.1 mL of extract and procedure proposed by Garcia-Mier, Jimenez-Garcia [8]. mixed for 45 seconds, and measurements were taken at Briefly, 200 μl of vanillin reagent (1% vanillin, 8% HCl in 730 nm after 15 minutes. +e antioxidant activity of the methanol) was added to 50 μl of methanolic extract and sample was calculated by determining the decrease in ab- placed in a 96-well plate; each sample was tested in triplicate. sorbance. Trolox was used as standard substance. +is assay Condensed tannins were quantified at 492 nm in a was based on the ability of different substances to scavenge Journal of Food Quality 3 radicals.