Characterization of New Polyphenolic Glycosidic Constituents and Evaluation of Cytotoxicity on a Macrophage Cell Line and Allelopathic Activities of Oryza sativa

Abstract

Four new constituents, as 5, 7-dihydroxy-4′-methoxyflavonol-3-O-β-d-arabinopyranosyl-(2′′→1′′′)-O-β-d-arabinopyrnosyl-2′′′-O-3′′′′, 7′′′′-dimethylnonan-1′′′′-oate (1), 5-hydroxy-7, 4′-dimethoxyflavone-5-O-α-d-arabinopyranosyl-(2"→1′′′)-O-α-d-arabinopyranosyl-2′′′-O-3′′′′, 7′′′′-dimethylnonan-1′′′′-oate (2), 5-hydroxy-7, 4′-dimethoxyflavone-5-O-β-d-arabinofuranosyl-(2"→1′′′)-O-β-d-arabinopyranosyl-2′′′-O-lanost-5-ene (3) and 4′,4′′-diferuloxy feruloyl-O-α-d-arabinopyranosyl-(2a→1b)-O-α-d-arabinopyranosyl-(2b→1c)-O-α-d-arabinopyranosyl-(2c→1d)-O-α-d-arabinopyranosyl-(2d→1e)-O-α-d-arabinopyranosyl-2e-3′′′, 7′′′-dimethylnonan-1′′′-oate (4), along with three known compounds (5–7) were isolated from Oryza sativa leaves and straw. The structures of new and known compounds were elucidated by 1D (1H and 13C NMR) and 2D NMR spectral methods, viz: COSY, HMBC, and HSQC aided by mass techniques and IR spectroscopy. The cytotoxicity of these constituents was assessed by using (RAW 264.7) mouse macrophage cell line, and allelopathic effects of compounds (1–7) on the germination and seedling growth characteristics such as seedling length and root length of barnyardgrass (Echinochloa oryzicola) were evaluated. Significant inhibitory activity was exhibited by compounds comprising flavone derivatives such as (1–3) on all of seed germination characteristics. The allelopathic effect of flavone derivatives were more pronounced on seedling length and root length than the germination characteristics. The higher concentration of flavone derivatives showed stronger inhibitory effects, whereas the lower concentrations showed stimulatory effects in some cases.

Chemical Structure Diversity and Extensive Biological Functions of Specialized Metabolites in Rice

“…Fifty-two diterpenoids (50-101) have been reported from rice [8,[17][18][19][20][21][22][23][24][25][26]37,[40][41][42][43][44][45][46][47][48]. Seven kinds of diterpenoid skeleton have been found in these diterpenoids: casbene (52-54), ent-cassadiene (56)(57)(58)(59)(60)(61), stemarene (62)(63)(64), pimarane (65)(66)(67)(68)(69)(70)(71)(72), pimaradiene (73)(74)(75)(76)(77)(78)(79)(80), entgibberellin (89)(90)(91), and kauranes (81-87 and 91-100) [8,…”

“…Thirty-five triterpenoids have been isolated and identified from rice, and are mainly found in rice bran [53][54][55][56][57][58][59][60][61][62][63][64][65][66]. The major types include citrostadienol (104)(105)(106)(107), gramisterol (108)(109)(110), cycloeucalenol (111)(112)(113), cycloartanol (114 and 115), tetracyclic triterpene (118)(119)(120), cycloartane (124)(125)(126)(127)(128), orizalanosterolide (130)(131), and lupane (132)(133) [53][54][55][56][57]61,[63][64][65]67,68]. Compounds 104-113 and their derivatives are considered to be nortriterpenoids according to their biosynthetic pathways.…”

“…Seventeen other phenolic compounds (356-372) have been identified from rice [64,82,92,[113][114][115][116][117]. These include tocopherols (358-361) and tocotrienols (362-365).…”

“…Twenty-six other types of compounds (414-439) have been identified from rice, including chain hydrocarbons (414-429, 438), alicyclic hydrocarbons (430, 432-437, 439), and aromatic hydrocarbons (431) [30,33,64,73,[135][136][137][138][139][140][141][142][143]. Compounds 419 and 435-437 are found throughout the whole rice plant.…”