## 5 Biological Activities of Rice Phytolexins
### Bioactivities of Phenolic Phytoalexins
Additionally, they found that sakuranetin reduced the proliferation rate of melanoma cells at concentrations \(\geq\)15 \(\upmu\)mol/L without directly affecting cell viability. Based on these findings, sakuranetin appears to be a promising candidate for anticancer drug development. In a study aimed at identifying antiallergic compounds in resin extracts of _Xanthorhoean hustilis_ R. BR. (Xanthorhoeaceae), [PERSON] and co-workers [85] isolated three chalcones and six flavonones, including sakuranetin, through bioassay-directed fractionation. In vivo assays and measurements of platelet aggregation demonstrated that sakuranetin is one of the active ingredients responsible for the antiallergic activity of _X. hustilis_ extracts. Between 1999 and 2005, several studies highlighted the presence of sesquiterpenes and flavonoids with anti-inflammatory activity in _Inula viscosa_ (L.) [PERSON] (Asteraceae), an herbaceous plant known for its effectiveness against skin inflammations [223; 224; 225; 226; 227; 228; 229; 230]. In 2007 [PERSON] and colleagues [223] tested the anti-inflammatory properties of three flavonones isolated from _I. viscosa_, namely 7-O-methylaromadendrin, 3-acetyl-7-O-methylaromadendrin, and sakuranetin. Sakuranetin was the most active in vitro, inhibiting the production of LTB4, acting directly on the 5-LOX enzyme and regulating secretory processes such as elastase release. Although the anti-inflammatory activity of flavonoids is usually related to their antioxidant activity, the results of [PERSON] et al. [223] suggest a possible non-redox inhibition of lipoxygenases, as well as a blockage of some proteins implicated in exocytotic mechanisms. [PERSON] and colleagues [224] observed that, even in the absence of adipogenic hormonal stimuli, sakuranetin strongly promoted both the differentiation of 3T3-L1 preadipocytes into adipocytes and the expression of genes associated with the development of adipocyte phenotypes. They also observed that glucose uptake in differentiated 3T3-L1 fat cells was stimulated by sakuranetin, suggesting that it may contribute to the maintenance of glucose homeostasis in animals. [PERSON] and co-workers [225] evaluated the impact of sakuranetin on vascular and lung parenchyma alterations in a murine model of chronic allergic pulmonary inflammation. In most of the parameters evaluated by histopathological analysis (Table 5), the effects of sakuranetin were similar to those of the steroidal anti-inflammatory drug dexamethasone. The authors speculated that the reduction in the number of eosinophils and elastic fibers in pulmonary vessels and lung parenchyma, promoted by sakuranetin, results from the reduction of oxidative stress and the levels of transcription factors NF-kB and VEGF in the lung. [PERSON] and collaborators [226] identified sakuranetin as a new inhibitor of the carrier protein \(\beta\)-hydroxyacyl-acyl dehydatase from _Helicobacter pylori_ (HpFabZ). Sakuranetin was compared with two other flavonoids that had already been reported as HpFabZ inhibitors, namely quercetin and apigenin [226]. Sakuranetin exhibited significantly greater inhibitory activity than the other compounds (IC\({}_{\mathbf{50}}\) in uM: 2.0, 39.3, and 11.0, respectively). Complex crystal structure analysis in combination with kinetic enzyme assays indicated that the compounds of interest act as competitive inhibitors of HpFabZ by binding to the B tunnel entrance of the substrate or by plugging into the C tunnel near the catalytic residues mainly through hydrophobic interactions and hydrogen-bond pattern. [PERSON] and colleagues [227] studied the activity of sakuranetin against promastigotes and amastigotes of _Leishman_ spp. and trypanastigotes and amastigotes of _Trypanosoma cruzi_. Sakurantin was found to be active against \(L\). _amazonensis_, _L. braziliensis_, _L. major_, and _L. chagasi_ (with IC\({}_{50}\) between 43 and 52 \(\mathrm{\SIUnitSymbolMicro/mL}\)) and against _T. cruzi_ Trypanastigotes (IC\({}_{50}\) = 20.17 \(\mathrm{\SIUnitSymbolMicro/mL}\)).