Herbicidal and Plant-growth Stimulating Effects of Phenolic Compounds Isolated from Lichens

The depsides atranorin (7) and diffractaic acid (1), the depsidones hypostictic (2) protocetraric (3), salazinic (4) acids, the xanthone secalonic acid (5), and usnic acid (6) were evaluated for their phytotoxic potentials against the target species Allium cepa cv. Baia periforme (onion, Monocotyledoneae). The bioassays, carried out under laboratory conditions, revealed that diffractaic (1) and hypostictic (2) acids stimulated plant growth; secalonic acid (5) stimulated seed germination and radicle growth, while reducing coleoptile length. Usnic acid (6) promoted seed germination and stronger inhibition of radicle and coleoptile growth. Protocetraric (3) and salazinic (4) acids and atranorin (7) exhibited a herbicidal effect, inhibiting seed germination and reducing radicle and coleoptile growth—features that suggest their utility as natural herbicides. These results invite further investigation to elucidate the mode of action of these compounds and to synthesize them for field experiments. DOI: http://dx.doi.org/10.17807/orbital.v7i3.75

Dormancy breakage of Stylosanthes humilis seeds by aluminium

Physiological dormancy of scarified seeds of Townsville stylo (Stylosanthes humilis HBK) was released by acidic aluminium (Al3+) solution. Antiethylenic substances inhibited germination of low-pH-stimulated dormant seeds, with a correspondingly low ethylene production and low activity of 1-aminocyclopropane-1-carboxylate (ACC) oxidase in seeds. On the other hand, antiethylenic substances did not decrease the germination of Al3+-stimulated seeds, but ACC oxidase activity and ethylene production by the seeds was decreased to a large extent. These data provide evidence that dormancy breakage by Al3+ differs from that caused by low pH and is not associated with ethylene production. Similarly to Al3+ action, methyl viologen (MV), a reactive oxygen species-generating compound, broke dormancy of Townsville stylo seeds. Sodium selenate and N-acetyl cysteine, antioxidant compounds, largely decreased germination of MV- and Al3+-stimulated dormant seeds. Altogether these data point to oxidative radicals constituting key molecules in the chain of events triggered by Al3+ leading to dormancy breakage

Ethnopharmacology of Fruit Plants: A Literature Review on the Toxicological, Phytochemical, Cultural Aspects, and a Mechanistic Approach to the Pharmacological Effects of Four Widely Used Species

Fruit plants have been widely used by the population as a source of food, income and in the treatment of various diseases due to their nutritional and pharmacological properties. The aim of this study was to review information from the most current research about the phytochemical composition, biological and toxicological properties of four fruit species widely used by the world population in order to support the safe medicinal use of these species and encourage further studies on their therapeutic properties. The reviewed species are: Talisia esculenta, Brosimum gaudichaudii, Genipa americana, and Bromelia antiacantha. The review presents the botanical description of these species, their geographical distribution, forms of use in popular medicine, phytochemical studies and molecules isolated from different plant organs. The description of the pharmacological mechanism of action of secondary metabolites isolated from these species was detailed and toxicity studies related to them were reviewed. The present study demonstrates the significant concentration of phenolic compounds in these species and their anti-inflammatory, anti-tumor, photosensitizing properties, among others. Such species provide important molecules with pharmacological activity that serve as raw materials for the development of new drugs, making further studies necessary to elucidate mechanisms of action not yet understood and prove the safety for use in humans