Abstract
Phthalic acid esters (PAEs) are a class of lipophilic chemicals widely used as plasticizers and additives to improve various products’ mechanical extensibility and flexibility. At present, synthesized PAEs, which are considered to cause potential hazards to ecosystem functioning and public health, have been easily detected in the atmosphere, water, soil, and sediments; PAEs are also frequently discovered in plant and microorganism sources, suggesting the possibility that they might be biosynthesized in nature. In this review, we summarize that PAEs have not only been identified in the organic solvent extracts, root exudates, and essential oils of a large number of different plant species, but also isolated and purified from various algae, bacteria, and fungi. Dominant PAEs identified from natural sources generally include di-n-butyl phthalate, diethyl phthalate, dimethyl phthalate, di(2-ethylhexyl) phthalate, diisobutyl phthalate, diisooctyl phthalate, etc. Further studies reveal that PAEs can be biosynthesized by at least several algae. PAEs are reported to possess allelopathic, antimicrobial, insecticidal, and other biological activities, which might enhance the competitiveness of plants, algae, and microorganisms to better accommodate biotic and abiotic stress. These findings suggest that PAEs should not be treated solely as a “human-made pollutant” simply because they have been extensively synthesized and utilized; on the other hand, synthesized PAEs entering the ecosystem might disrupt the metabolic process of certain plant, algal, and microbial communities. Therefore, further studies are required to elucidate the relevant mechanisms and ecological consequences.
Highlights
Phthalic acid esters (PAEs) are common plasticizers added to polymeric materials to improve their flexibility and workability [1]
Huang et al (2017) [116] analyzed the extracts of aerial parts plants, root exudates, and plant rhizosphere soil of Chrysanthemum indicum to determine the effect of the allelochemical diethyl phthalate, and the results show that it has a noticeable impact on promoting the fresh weight of lettuce, as well as the root growth of lettuce and rape
PAEsininthe theenvironment environmentare aremainly mainly derived from chemical syntheses that are applied in building materials, care products, medical equipment, and children’s toys, etc., which are convenient for human production and life [19,27,132]
Summary
Phthalic acid esters (PAEs) are common plasticizers added to polymeric materials to improve their flexibility and workability [1]. 80% of the phthalates made in the European Union and China, respectively [7] With such extensive application of phthalate-containing products, PAEs have attracted increasing attention as environmental and biomedical pollutants, which may invisibly enter the human body through airborne transmission, skin contact, and food chain transmission, constituting potential health and ecological system threats [8]. (2014) reported that di-n-butyl and di(2-ethylhexyl) phthalate disrupted the antioxidant system of carps, combined exposure to these two compounds exacerbated this change [15]. What remains unclear is that in many cases, it is rather complicated to determine whether these compounds come from synthesized materials that later cause contamination of the air, water, or soil, or whether they may be produced by the plants and microorganisms themselves. The objective of this review is to summarize the plant and microorganism origin of PAEs so as to better understand their possible sources: Are they synthesized chemicals, or are they naturally occurring secondary metabolites?
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