Plant Growth Inhibitory Activity of p-Hydroxyacetophenones and Tremetones from Chilean Endemic Baccharis Species and Some Analogous:  A Comparative Study

Abstract

Plant growth inhibitory effects of acetophenones 1-6, tremetones 7-12, and MeOH and CH(2)Cl(2) extracts from the aerial parts of Baccharis linnearis, Baccharis magellanica, and Baccharis umbelliformis collected in Chile were assayed as growth inhibitory activity in ranges of 10-500 microM and 0.1-150 ppm, respectively. The effects on seedling growth, germination, and respiration of ryegrass, lettuce, green tomato, and red clover weedy target species were measured. In addition to the inhibitory activity on bleaching of crocin induced by alkoxyl radicals, these compounds also demonstrated scavenging properties toward 2,2-diphenyl-1-picrylhydrazyl in thin-layer chromatography autographic and spectrophotometric assays. In addition, acetophenones and tremetones also showed inhibition of H(+) uptake and oxygen uptake respiration in isolated chloroplasts and mitochondria, respectively. Our results indicate that 1, 4, 7-12, and CH(2)Cl(2) extracts interfere with the dicot preemergence properties, mainly energy metabolism of the seeds at the level of respiration. These compounds appear to have selective effects on the radicle more than shoot growth of dicot seeds. Also, the levels of radicle inhibition obtained with some compounds on Physalis ixocarpa and Trifolium pratense are totally comparable to those of ovatifolin, a known natural growth inhibitor. This behavior might be responsible for its plant growth inhibitory properties and its possible role as an allelopathic agent.

Phytotoxic activities of (2R)-6-hydroxytremetone

“…Overall, (2R)-6-hydroxytremetone was a potent inhibitor of seed germination as shown by an inhibition of approximately 80% in the germination of all species except for wheat when 100 mg l À1 of the compound was tested. Our results are in agreement with a previous study, which has reported an inhibition of 100% in dicotyledoneous seed germination by the isomer 4-hydroxytremetone isolated from Baccharis, another genus of the Asteraceae family [10]. Interestingly, our isolated compound (2R)-6-hydroxytremetone showed different effects when tested on monocotyledoneous.…”

“…These results are in agreement with the potent inhibition activity reported on seed germination of the monocotyledoneous Echinochloa and the dicotyledoneous Amaranthus [12], but in this work euparin (5-acetyl-6-hydroxy-2-isopropenylbenzofuran), another benzofuran derivative was assayed. Although Céspedes et al [10] assayed the monocotyledoneous ryegrass, no data related to the effect of 4-hydroxytremetone on seed germination has been provided in their work. On the other hand, the use of the PD index allows us to evaluate the economical impact of a chemical compound from an agricultural point of view as decreases in the seed germination undoubtedly represents a profit loss for the farmers when the crops are invaded with members of this family.…”

“…However, beneficial effects such as bacterial growth inhibition, antitumor, and anti-HIV activities have been also reported [7e9]. Hydroxytremetones have been previously isolated from the genus Baccharis [10], Encelia [2], Eupatorium [8], Geraea [11], Helianthella [12], Liatris [13], Ligularia [14], Tagetes [15], and Xenophyllum [16].…”

Polygala extraaxillaris: oxidative stress in Brachiaria decumbens mediated by volatile oils

“…These results confirm the investigations regarding inhibition of ATP formation, proton capture and the rate of electron transport by the activity of phydroxyacetophenone (Céspedes et al, 2002), determining that the presence of oxygenated functions (hydroxyl) significantly increases the inhibitory potential of these compounds. Consequently, these radicals may directly affect the permeability of cell membranes, causing damage to DNA and proteins and leading to changes in germination and growth of the investigated species.…”

Fungistatic Activity Of Essential Oils Extracted from Peumus boldus Mol., Laureliopsis philippiana (Looser) Schodde and Laurelia sempervirens (Ruiz & Pav.) Tul. (Chilean Monimiaceae)

“…Leaves from each species under study were snipped and essences were extracted by hydrodistillation as established by Montes et al (2001) and Céspedes et al (2002).…”