Hypoglycemic effect and bioactive compounds associated with the ripening stages of the Cucurbita ficifolia Bouché fruit

Mexican Plants Involved in Glucose Homeostasis and Body Weight Control: Systematic Review

BACKGROUND

Obesity is defined as abnormal or excessive fat accumulation, provoking many different diseases, such as obesity and type 2 diabetes. Type 2 diabetes is a chronic-degenerative disease characterized by increased blood glucose levels. Obesity and type 2 diabetes are currently considered public health problems, and their prevalence has increased over the last few years. Because of the high cost involved in the treatment of both diseases, different alternatives have been sought. However, the general population uses medicinal plants, in the form of tea or infusions, to treat different diseases. Therefore, traditional medicine using medicinal plants has been investigated as a possible treatment for type 2 diabetes and body weight control.

AIM OF THE STUDY

The purpose of this review is to find medicinal plants used in Mexico that could exert their beneficial effect by regulating insulin secretion and body weight control.

MATERIAL AND METHOD

For the development of this review, Mexican plants used in traditional medicine to treat type 2 diabetes and body weight control were searched in PubMed, Google Scholar, and Scopus. The inclusion criteria include plants that presented a significant reduction in blood glucose levels and/or an increase in insulin secretion.

RESULTS

We found 306 Mexican plants with hypoglycemic effects. However, plants that did not show evidence of an increase in insulin secretion were eliminated. Finally, only five plants were included in this review: Momordica charantia L. (melón amargo), Cucurbita ficifolia bouché (chilacayote), Coriandrum sativum L. (cilantro), Persea americana Mill. (aguacate) Bidens pilosa (amor seco), including 39 articles in total. Here, we summarized the plant extracts (aqueous and organic) that have previously been reported to present hypoglycemic effects, body weight control, increased secretion and sensitivity of insulin, improvement of pancreatic β cells, and glucose tolerance. Additionally, these effects may be due to different bioactive compounds present in the plants' extracts.

CONCLUSION

Both in vivo and in vitro studies are required to understand the mechanism of action of these plant extracts regarding insulin secretion to be used as a possible treatment for type 2 diabetes and body weight control in the future.

Phenolic compounds and antioxidant activity in Cucurbita ficifolia fruits, an underrated fruit

The fruits and seeds of Cucurbita ficifolia Bouché are sources of minerals, vitamins, and functional compounds with nutraceutical and preventive potential against cardiovascular diseases and diseases derived from eating disorders. C. ficifolia is native from Mesoamerica and is currently cultivated in temperate zones from Mexico to South America and Asia. This study evaluated the fruit mesocarps of C. ficifolia for physicochemical parameters, antioxidant activity, and phenolic compound contents in a collection of farmers' landraces. Germplasm is cultivated by traditional farmers in the temperate zones of two municipalities from Oaxaca, Mexico. The results show that the content of soluble solid contents (SSC), pH, total sugars (TS), and flavonoids are influenced by the fruit geographical origin (municipalities) and implicitly by their agroecological cultivation conditions (Huamelúlpam: SSC = 6.22 °Brix, pH = 5.44, TS = 0.52 mg G g-1, flavonoids = 1.24 mg CE g-1; Yanhuitlán: SSC = 6.69, pH = 5.33, TS = 0.55, flavonoids = 1.30). Among populations preserved by traditional farmers, significant differences, and wide variability were found for all parameters evaluated (Huamelúlpam: SSC = 4.9-7.3, pH = 5.5-5.8, TS = 0.4-0.7, protein = 5.8-11.4, polyphenols = 1.9-4.8, flavonoids = 1.0-1.5, DPPH = 4.3-10.6, and FRAP = 4.8-11.8; Yanhuitlán: SSC = 4.3-8.9, pH = 4.8-5.6, TS = 0.4-0.7, protein = 5.0-15.3, polyphenols = 1.9-4.9, flavonoids = 0.8-1.9, DPPH = 5.3-10.5, and FRAP = 4.5-12.6). Eight compounds were identified by UPLC-MS: L-phenylalanine, an amino acid that is regularly associated with proteins; vanillin, a phenolic aldehyde with its functional groups including aldehyde, hydroxyl, and ether; and six phenolic acids: 4-hydroxybenzoic acid, 4-hydroxyphenylacetic acid, vanillic acid, 4-coumaric acid, ferulic acid, and salicylic acid, all with potential health effects. The C. ficifolia fruit mesocarp has bioactive compounds with high antioxidant activity with the potential to both improve diet and to obtain other benefits against nontransmissible diseases derived from food and its associated risk factors.

Chayote Fruit (Sechium edule var. virens levis) Development and the Effect of Growth Regulators on Seed Germination

The chayote fruit is a nontraditional vegetable belonging to the Cucurbitaceae family. The fruit has an endocarpic recalcitrant seed that emerges postharvest, drastically shortening its shelf life. In this study, the changes during fruit and seed development before and after harvest (ah) are reported. Additionally, in order to investigate how growth regulators (GRs) affect seed germination, 2-cloroethylphosphonic acid (CPA) (200 µL L^-1), gibberellic acid (GA₃) (100 and 200 mg L^-1), auxin (2,4-D) (0.5 and 1.0 mM), and abscisic acid (ABA) (0.5 and 1.0 mM) were applied after harvest. The results showed that the chayote fruit reached horticultural maturity at 21 days after anthesis, with a sigmoid trend: phase I featured slow growth and high transpiration; in phase II, growth was accelerated and accumulation of endosperm was observed; and in phase III, both growth rate and transpiration were reduced, soluble sugars increased, and the seed showed 25% cotyledon development. At day 13 ah, CPA, GA₃, and 2,4-D (0.5 mM) increased seed germination, with values between 10 and 15 mm of the embryonary axis, and the treatments with 2,4-D (1 mM) and ABA (0.5 and 1.0 mM) retarded their growth (2-6 mm). This research allowed us to reveal the phenological phases and the shelf life of the chayote fruit, as well as the results of possible postharvest treatment with GRs; our results suggest that strategies to delay viviparism and prolong the shelf life of the fruit should be applied before 10 days ah, when the embryonic axis of the seed has not developed.

Fermentation of the Cucurbita ficifolia Fruit Juice: Its Antioxidant Activity and Effects on the Glycemia

Cucurbita ficifolia is an edible plant whose fruits have hypoglycemic, anti-inflammatory, and antioxidant activities. Fermentation might improve these properties. This research aims to perform and characterize its fermentation in native and induced conditions with Lactobacillus plantarum (Lp) and evaluate its antioxidant activity and effect on glycemia. Fresh juice from mature fruits was characterized. One portion of this juice was spontaneously left to ferment (native fermentation), and the other was inoculated with Lp (controlled fermentation). Fermentation was monitored each 8 h by 56 h to measure microbial growth, pH, acidity, sugars, soluble protein, polyphenols and flavonoids, antioxidant activity, and effects on glycemia. In native fermentation, the growth of total microorganisms increased up to 32 h, decreasing at the end of the process. In Lp fermentation, total microorganisms increased until 16 h to stay constant at the end, with a predominance of Lp. The pH and the sugars decreased in the two fermentations, while polyphenol and flavonoid increased. In spontaneous fermentation, these changes were lesser. Both fermentations, like fresh juice, preserve functional properties (antioxidant, alpha-glucosidase inhibition, and hypoglycemia). The fermentation of this juice with Lp may develop functional beverages, which is significant due to its consumption as an edible fruit with medicinal properties.

4-Hydroxybenzoic Acid and β-Sitosterol from Cucurbita ficifolia Act as Insulin Secretagogues, Peroxisome Proliferator-Activated Receptor-Gamma Agonists, and Liver Glycogen Storage Promoters: In Vivo, In Vitro, and In Silico Studies

Insulin secretion and GLUT4 expression are two critical events in glucose regulation. The receptors G-protein-coupled receptor 40 (GPR40) and peroxisome proliferator-activated receptor-gamma (PPARγ) modulate these processes, and they represent potential therapeutic targets for new antidiabetic agent's design. Cucurbita ficifolia fruit is used in traditional medicine for diabetes control. Previous studies demonstrated several effects: a hypoglycemic effect mediated by an insulin secretagogue action, antihyperglycemic effect, and promoting liver glycogen storage. Anti-inflammatory and antioxidant effects were also reported. Moreover, some of its phytochemicals have been described, including d-chiro-inositol. However, to understand these effects integrally, other active principles should be investigated. The aim was to perform a chemical fractionation guided by bioassay to isolate and identify other compounds from C. ficifolia fruit that explain its hypoglycemic action as insulin secretagogue, its antihyperglycemic effect by PPARγ activation, and on liver glycogen storage. Three different preparations of C. ficifolia were tested in vivo. Ethyl acetate fraction derived from aqueous extract showed antihyperglycemic effect in an oral glucose tolerance test and was further fractioned. The insulin secretagogue action was tested in RINm5F cells. For the PPARγ activation, C2C12 myocytes were treated with the fractions, and GLUT4 mRNA expression was measured. Chemical fractionation resulted in the isolation and identification of β-sitosterol and 4-hydroxybenzoic acid (4-HBA), which increased insulin secretion, GLUT4, PPARγ, and adiponectin mRNA expression, in addition to an increase in glycogen storage. 4-HBA exhibited an antihyperglycemic effect, while β-sitosterol showed hypoglycemic effect, confirming the wide antidiabetic related results we found in our in vitro models. An in silico study revealed that 4-HBA and β-sitosterol have potential as dual agonists on PPARγ and GPR40 receptors. Both compounds should be considered in the development of new antidiabetic drug development.

The complete chloroplast genome sequence of the Cucurbita ficifolia Bouché (Cucurbitaceae)

Cucurbita ficifolia Bouché is an important germplasm resource used for rootstock and hypoglycemic food in Cucurbitaceae. The complete chloroplast genome sequence of C. ficifolia has been determined in this study. The total genome size is 157,533 bp in length and contains a pair of inverted repeats (IRs) of 25,639 bp, which were separated by large single copy (LSC) and small single copy (SSC) of 88,112 bp and 18,143 bp, respectively. A total of 130 genes were predicted including 86 protein-coding genes, eight rRNA genes and 36 tRNA genes. Further, Maximum-likelihood phylogenetic analysis revealed that C. ficifolia is a base clade of genus Cucurbita and closer to Cucurbita maxima. The chloroplast genome of C. ficifolia would promote the germplasm exploration, phylogenetic relationships, and molecular biology researches in Cucurbita.