Bioactive Compounds and Antioxidant Capacity of Valencian Pepper Landraces

Abstract

Sweet pepper is one of the most important economic fruits with nutritional attributes. In this sense, the nutraceutical value of consumed products is a major concern nowadays so the content of some bioactive compounds and antioxidants (phenols, ascorbic acid, lycopene, carotenoids, chlorophylls, and antioxidant activity) was monitored in 18 sweet pepper landraces at two maturity stages (green and red). All the traits except chlorophylls significantly increased in red fruits (between 1.5- and 2.3-fold for phenols, ascorbic acid, and 2-2-diphenyl-1-picrylhydrazyl (DPPH) inhibition activity, 4.8-fold for carotenoid and 27.4-fold for lycopene content), which suggests that ripening is key for obtaining desired fruit quality. Among landraces, P-44 in green fruits is highlighted for its content in carotenoids, chlorophylls, phenols, and ascorbic acid, and P-46 for its antioxidant capacity and lycopene content. Upon maturity, P-48, P-44, and P-41 presented higher levels of phenols and lycopene, and P-39 of phenols, carotenoid, and DPPH. This work reflects a wide variability in the 18 pepper landraces at bioactive compounds concentration and in relation to fruit ripeness. The importance of traditional landraces in terms of organoleptic properties is emphasized as they are the main source of agricultural biodiversity today and could be helpful for breeders to develop new functional pepper varieties.

Keywords: antioxidant activity; ascorbic acid; bioactive compound; carotenoids; landrace; lycopene; pepper; phenols.

Figure 1

Total phenols (A,B), total ascorbic acid concentration (C,D), and lycopene concentration (E,F) in the green (A,C,E) and red (B,D,F) fruit produced by the 18 pepper landraces. Values are the mean ± SE of four replicates per landrace. Mean is subjected to a one-way ANOVA and different letters indicate significant differences at p < 0.05 using the LSD test.

Figure 2

Carotenoid (A,B), chlorophyll a + b (C,D), and antioxidant capacity (E,F) in the green (A,C,E) and red (B,D,F) fruit produced by the 18 pepper landraces. Values are the mean ± SE of four replicates per landrace. Mean is subjected to a one-way ANOVA and different letters indicate significant differences at p < 0.05 using the LSD test.

Figure 3

Linear correlation coefficient (r) and its significance for fruit traits (A) in green and (B) red fruits in the collection of the 18 pepper landraces cultivated in Spain. ***, ** and * indicate significance at p < 0.001, p < 0.01, p < 0.05, respectively.

Figure 4

Similarities among green fruits belonging to the 18 pepper accessions evaluated based on six traits (total phenolics, ascorbic acid, carotenoid, lycopene, and chlorophyll content, DPPH scavenging activity) represented the two first components (first component, x-axis; second component, y-axis) of the principal components analysis (43.3% and 28.8% of the total variation, respectively).

Figure 5

Similarities among red fruits belonging to the 18 pepper accessions evaluated based on six traits (total phenolics, ascorbic acid, carotenoid, lycopene and chlorophyll content, DPPH scavenging activity) represented in (A) the two first components (first component, x-axis; second component, y-axis) of the principal components analysis (33.6% and 20.3% of total variation, respectively); and (B) the first and third components (first component, x-axis; third component, y-axis) of the principal components analysis (33.6% and 17.1% of the total variation, respectively).

Figure 6

Pepper fruits in different maturity stages (red and green) obtained from the cultivated landraces. The size of the grid cells in the fruit pictures is 1 cm × 1 cm.