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This study evaluated the phytotoxic potential and antioxidant activity of Tagetes patula and Tagetes erecta, and total phenols and flavonoids of the extracts were quantified. Laboratory bioassays for both pre-and postemergence were performed in Lactuca sativa L. seeds and in the Allium cepa seeds test. The antioxidant activity was evaluated by DPPH radical scavenging and reducing power of iron, besides total phenols and flavonoids quantification in the extracts. Thus, was observed a reduction in the mitotic index when in compared with the negative control. Was observed also a reduction the germination and development of tested seedlings and was verified a considerable antioxidant potential and presence of flavonoids and phenolic compounds in the extracts. According to these results, it is possible to conclude that T. erecta and T. patula have phytotoxic compounds that may enhance and expand their use in the management of organic agriculture, mainly in vegetables.

The eutrophication of aquatic ecosystems is a serious environmental problem that leads to increased frequency of cyanobacterial blooms and concentrations of cyanotoxins. These changes in aquatic chemistry can negatively affect animal and human health. Environment-friendly methods are needed to control bloom forming cyanobacteria. We investigated the effect of Hordeum vulgare L. (barley) straw degradation extract and its fractions on the growth, oxidative stress, antioxidant enzyme activities, and microcystins content of Microcystis aeruginosa (Kützing) Kützing BCCUSP232. Exposure to the extract significantly (p<0.05) inhibited the growth of M. aeruginosa throughout the study, whereas only the highest concentration of fractions 1 and 2 significantly (p<0.05) reduced the growth of the cyanobacterium on day 10 of the experiment. The production of reactive oxygen species (ROS), lipid peroxidation and antioxidant enzyme activities were significantly (p<0.05) altered by the extract and fractions 1 and 2. Phytochemical profiling of the extract and its fractions revealed that the barley straw degradation process yielded predominantly phenolic acids. These results demonstrate that barley straw extract and its fractions can efficiently interfere with the growth and development of M. aeruginosa under laboratory conditions.

Edited by L VerschaeveKeywords: Phytotoxic Allelopathy Allelochemicals HPLC -PAD Allium cepa DPPH Among the numerous plant species occurring in the Cerrado, Ouratea spectabilis stands out because of the lack of species that grow beneath its canopy. Therefore, this study aimed to evaluate the phytotoxic potential of different extracts and fractions of the hydroethanolic extract from leaves of O. spectabilis through laboratory bioassays of the pre-and post-emergence of seeds of Lactuca sativa L., determination of the mitotic index in root cells of Allium cepa L., antioxidant activity and phytochemical screening of different classes present in extracts and ethyl acetate fractions. It was possible to verify that different extracts and ethyl acetate fractions of O. spectabilis interfered with germination rates, as reduced germination was observed when compared with the control. Similarly, growth and development was affected in lettuce seedlings, as shown by the reduced length of primary roots and hypocotyls compared with the control. In addition, the mitotic index was reduced in treated groups compared with the negative control. HPLC-PAD analysis for both the hydroethanolic extract and its ethyl acetate fraction, showed a predominance of flavonoid compounds belonging to the groups of isoflavones and catechins in ethyl acetate fractions of hydroethanolic extracts. Thus, it was concluded that this species synthesizes phytotoxic compounds capable of interfering in the stabilization and development of other species.

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