Screening of Chilli Pepper Genotypes as a Source of Capsaicinoids and Antioxidants under Conditions of Simulated Drought Stress

Abstract

In many regions of the world, the production of vegetable crops is limited by a deepening water crisis. Drought stress affects productivity and the chemical composition of crops. The variability of drought tolerance between species and cultivars of economically important crops, such as pepper (Capsicum species), requires specific investigations to understand the physiological and biochemical responses to the aftermath of drought. The fruits and leaves of four chilli pepper cultivars were investigated to elucidate the fruits' pungency (Scoville Heat Units, SHU), ascorbic acid content, DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, polyphenol content, membrane lipid peroxidation and key protective antioxidant enzyme activity under drought stress (18-28% volumetric water content) as compared to the control (35-60%). Drought increased the chilli pepper fruits' pungency expressed in Scoville Heat Units (SHU) as well as ascorbic acid content, but this relationship was also dependent on genotype and stress duration. 'Jolokia' was marked as most sensitive to drought by increasing content of capsaicinoids and DPPH • scavenging activity under stress conditions. Capsaicinoids and Ascorbic acid (AsA) greatly influenced the antioxidant activity of highly pungent chilli pepper fruits, although total phenols played a significant role in the mildly pungent genotypes. Generally, the activities of antioxidant enzymes increased under drought in chilli pepper leaves and fruits, although the intensity of the reaction varied among the cultivars used in the current research. All the investigated biochemical parameters were involved in the drought response of chilli pepper plants, but their significance and effectiveness were highly cultivar-dependent.Plants 2020, 9, 364 2 of 17 substrates, fertigated, and bell pepper canopy training is a common practice. The chilli pepper is cultivated without training. The container growing cost is higher, but it decreases the risk of adjacent plant contamination with root-borne diseases [2,3].Chilli pepper is added to dishes in small amounts, but the intake of chilli even as a spice enriches the diet with polyphenols and other bioactive compounds, especially ascorbic acid and other vitamins, carotenoids (α-and β-carotene), capsaicinoids and mineral salts [4]. The most characteristic phytochemicals of all members of the genus Capsicum are capsaicinoids, compounds providing the pungent taste but also of exhibiting antioxidant activity [5]. There is a growing interest in the enhancement of compounds in food having health-promoting attributes such as antioxidants, and which were previously regarded as non-nutritive, including phenolic compounds (simple phenols, flavonoids, anthocyanins, lignans and lignins, stilbenes and tannins). Phenols are antioxidants in nature, often associated with plant defence against biotic and abiotic stress factors. Additionally, phenols modify fruit colour, taste, aroma and flavour, and also provide health-beneficial effects for humans [6,7].Variability in ...

Antioxidant Profile of Pepper (<em>Capsicum annuum</em> L.) Fruits Containing Diverse Levels of Capsaicinoids

“…As an appraisal of the potential roles attributed to ascorbate in pepper fruits, it was proposed that in the sweet varieties, ascorbate functions as a redox buffer to balance the great metabolic changes which undergo during ripening [5,7]. Regarding the hot varieties (Padrón and Alegría), the pattern observed in this work where ascorbate levels increased in those fruits was also reported earlier for diverse hot pepper varieties [14,18,50,91]. Perhaps, the redox stabilizing role of ascorbate indicated above for sweet pepper could be also applicable to hot varieties to assure the capsaicinoids level.…”

“…Excepting Alegría which has been scarcely used for research purposes, reports on the other three varieties can be found in the literature. Thus, Melchor variety has been used to decipher the mechanisms involved in fruit ripening [18,39,66,67] where some of their antioxidant system have been reported to be involved [68]. Variety Piquillo was used as model to address the effects triggered by infection with Verticillum [69][70][71][72] and how to protect pepper plants against it through diverse practices [73,74], as well as to investigate the effect of sanitized sewage sludge on the growth, yield, fruit quality, soil microbial community and the physiology of pepper plants [75,76].…”

“…In pepper fruits containing these alkaloids this feature is quite interesting since these horticultural products are one of those with the highest ascorbate levels [5], with ascorbate being perhaps the most paradigmatic molecular antioxidant for living beings. In fact, ascorbate is one of the parameters which is commonly determined in (sweet and hot) pepper fruit research either considering ripening and post-harvest, any type of stress (biotic, abiotic and environmental), or culture practices [4,5,7,11,14,18,46,48,50,76,85,91]. As an appraisal of the potential roles attributed to ascorbate in pepper fruits, it was proposed that in the sweet varieties, ascorbate functions as a redox buffer to balance the great metabolic changes which undergo during ripening [5,7].…”

“…According to the pungent level, pepper fruits are ranked in the so-called Scoville scale which assigns a score to each fruit variety. In this scale, the highest value for the most pungent pepper fruit variety is around 3 • 10 6 , being pure capsaicin 16 • 10 6 [14][15][16][17][18][19]. Capsaicin is an alkaloid with phenylpropanoid nature which has given rise to a family of capsaicinoids composed by, at least 22 primary compounds.…”

Antioxidant Profile of Pepper (Capsicum annuum L.) Fruits Containing Diverse Levels of Capsaicinoids

“…According to the pungent level, pepper fruits are ranked on the so-called Scoville scale which assigns a score to each fruit variety. In this scale, the highest value for the most pungent pepper fruit variety is around 3 × 10 6 , pure capsaicin being 16 × 10 6 [14][15][16][17][18]. Capsaicin is an alkaloid with a phenyl-propanoid nature which has given rise to a family of capsaicinoids composed of at least 22 primary compounds.…”