Carrots are a multi-nutritional food source. They are an important root vegetable, rich in natural bioactive compounds, which are recognised for their nutraceutical effects and health benefits. This review summarises the occurrence, biosynthesis, factors affecting concentration, and health benefits of phytochemicals found in Daucus carota. Two hundred and fifty-five articles including original research papers, books, and book chapters were analysed, of which one hundred and thirty articles (most relevant to the topic) were selected for writing the review article. The four types of phytochemicals found in carrots, namely phenolics, carotenoids, polyacetylenes, and ascorbic acid, were summarised. These chemicals aid in the risk reduction of cancer and cardiovascular diseases due to their antioxidant, anti-inflammatory, plasma lipid modification, and anti-tumour properties. Numerous factors influence the amount and type of phytochemicals present in carrots. Genotype (colour differences) plays an important role; high contents of α and β-carotene are present in orange carrots, lutein in yellow carrots, lycopene in red carrots, anthocyanins in the root of purple carrots, and phenolic compounds abound in black carrots. Carotenoids range between 3.2 mg/kg and 170 mg/kg, while vitamin C varies from 21 mg/kg to 775 mg/kg between cultivars. Growth temperatures of carrots influence the level of the sugars, carotenoids, and volatile compounds, so that growing in cool conditions results in a higher yield and quality of carrots, while higher temperatures would increase terpene synthesis, resulting in carrots with a bitter taste. It is worthwhile to investigate the cultivation of different genotypes under various environmental conditions to increase levels of phytochemicals and enhance the nutritional value of carrot, along with the valorisation of carrot by-products.

The objective of the present study was to determine the effect of the application of a nanoemulsion made of orange essential oil and Opuntia oligacantha extract on avocado quality during postharvest. The nanoemulsion was applied as a coating in whole fruits, and the following treatments were assessed: concentrated nanoemulsion (CN), 50% nanoemulsion (N50), 25% nanoemulsion (N25) and control (C). Weight loss, firmness, polyphenol oxidase (PPO) activity, total soluble solids, pH, external and internal colour, total phenols, total flavonoids, antioxidant activity by 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH), while the structural evaluation of the epicarp was assessed through histological cuts. Significant differences were found (p < 0.05) among the treatments in all the response variables. The best results were with the N50 and N25 treatments for firmness and weight loss, finding that the activity of the PPO was diminished, and a delay in the darkening was observed in the coated fruits. Furthermore, the nanoemulsion treatments maintained the total phenol and total flavonoid contents and potentiated antioxidant activity at 60 days. This histological study showed that the nanoemulsion has a delaying effect on the maturation of the epicarp. The results indicate that using this nanoemulsion as a coating is an effective alternative to improve the postharvest life of avocado.

In this study Amaranthus cruentus plants were grown under controlled optimal conditions (28/21 °C) for three months and then subjected to cold (14/7 °C) and hot (33/40 °C) temperatures. We investigated the influence of these temperature regimes on the metabolite profile of the leaves through analyses of data by TLC, HPLC and GC-MS spectrometry. The phytotoxic potential of a methanol-water (MW) and dichloromethane (DCM) extract from the aerial parts were examined through in vitro screening of germination and growth of lettuce and pepper. The optimal extracts displayed the highest diversity of secondary metabolites, and the highest total phenolics and flavonoids content. Through TLC and HPLC analysis the significantly lower phenolic content in the hot temperature treated samples was confirmed. A wide range of metabolites were detected in the DCM extracts through GC-MS analyses. The phytotoxicity of both the MW and DCM extracts were demonstrated, as germination and growth of pepper and lettuce were significantly inhibited, indicating the presence of more than one allelochemical compound which may affect the allelopathic activity of A. cruentus during changes in environmental temperatures.

The relationships between allelochemicals and environmental factors are a key factor for the growth of plants under rotation. We investigated the allelopathic potential of Amaranthus cruentus L, grown under different temperature conditions in in vitro bioassays. An inhibitory effect on germination and growth of lettuce (Lactuca sativa L.), tomato (Solanum lycopersicum L.), pepper (Capsicum annuum L.) and cucumber (Cucumis sativus L.) was observed when seeds were subjected to the leaf litter of Amaranthus cruentus. Analysis from our study indicated that germination percentage was significantly affected by growth temperatures (T) of the amaranth (P ˂ 0.0001), litter concentration (C) (P ˂ 0.0001), vegetable type (V) (P ˂ 0.0001), the T × V interaction (P = 0.0041) and V × C interaction (P ˂ 0.0001). Pepper was the most sensitive with a decline in germination percentage at increasing concentrations (0, 1 and 5 mg ml^-1) of litter. Hypocotyl and seminal root lengths were adversely influenced by the plant litter for all the temperature treatments, although effects were most severe when exposed to the leaf litter of the hot temperature treatment. The inhibition caused by the litter was dependent on growth temperature and concentration, while each vegetable species showed different levels of sensitivity.