β-Glucosidase Involvement in the Bioactivation of Glycosyl Conjugates in Plants: Synthesis and Metabolism of Four Glycosidic Bond Conjugates in Vitro and in Vivo

Abstract

Mobile glucose-pesticide conjugates in the phloem are often restricted by decreases in biological activity. However, plants can bioactivate endogenous glucosides, which are assumed as able to bioactivate exogenous conjugates. In this study, four glycosidic bonds (O-, S-, N-, and C-glycosidic bonds) of glucose-pesticide conjugates were designed and synthesized, and then metabolism assays were carried out in vitro and in vivo. Results showed that β-glucosidases played a role in the hydrolysis of O-glycosidic bond conjugates in Ricinus communis L. The liberated aglycons possessed insecticidal activities against Plutella xylostella L. and Spodoptera litura F. These results could help establish methods of circumventing the mutual exclusivity of phloem mobility and biological activity by hydrolyzing endogenous β-glucosidases.

Vectorizing agrochemicals: enhancing bioavailability via carrier‐mediated transport

“…48 In addition, endogenous ß-glucosidases were involved in the hydrolysis of a glucose-fipronil conjugate with an O-glycosidic bond, which can achieve the enzymatic release of the active aglycone. 57 The enzymatic deglycolysation in vitro can be modulated by adjusting the linker length of the conjugate, and the in vivo insecticidal bioassay supports that the active aglycones are released from the conjugates after root absorption and exhibit the same level of activity as fipronil. 68 Several attempts mentioned above suggest that the carrier-mediated propesticide approach of conjugation with a nutrient moiety is a feasible approach to confer systemic properties to non-mobile agrochemicals.…”

“…Systemicity studies showed that the uptake of glucose‐fipronil by cotyledon discs was markedly inhibited by carbonyl cyanide 3‐chlorophenylhydrazone (CCCP), glucose, and phloridzin, and its phloem mobility was inhibited by phloridzin, suggesting that a carrier‐mediated mechanism was involved in uptake and phloem loading . In addition, endogenous ß‐glucosidases were involved in the hydrolysis of a glucose‐fipronil conjugate with an O ‐glycosidic bond, which can achieve the enzymatic release of the active aglycone . The enzymatic deglycolysation in vitro can be modulated by adjusting the linker length of the conjugate, and the in vivo insecticidal bioassay supports that the active aglycones are released from the conjugates after root absorption and exhibit the same level of activity as fipronil .…”

The linker length of glucose–fipronil conjugates has a major effect on the rate of bioactivation by β‐glucosidase

“…Third‐instar stage larvae of P. xylostella were prepared in the laboratory. The insecticidal activities of aglycones and fipronil against P. xylostella were evaluated using a previously described leaf‐dipping bioassay with some modifications . All compounds were dissolved in dimethyl sulfoxide and diluted with distilled water containing TW‐80 to obtain 1.25, 0.63, and 0.31 mg L −1 for bioassays.…”

“…The existence of the β‐glucosidase‐based two‐component plant defense system has prompted an exploration of the feasibility of exploiting endogenous β‐glucosidase activity to hydrolyze glucose–pesticide conjugates, thereby supplementing the plants' native chemical defenses with a phloem mobile pesticide. It has been established that glucose–fipronil conjugates can be hydrolyzed in planta , resulting in the release of biologically active aglycones . However, there is a significant difference in the efficiency of hydrolysis between the two glucose‐fipronil conjugates, GOF ( N ‐{3‐cyano‐1‐[2,6‐dichloro‐4‐(trifluoromethyl) phenyl]‐4‐[(trifluoromethyl)‐sulfinyl]‐1 H ‐pyrazol‐5‐yl}‐2‐aminoethyl‐ β ‐ d ‐glucopyranoside) and GOTF ( N ‐{3‐cyano‐1‐[2,6‐dichloro‐4‐(trifluoromethyl) phenyl]‐4‐[(trifluoromethyl) sulfinyl]‐1 H ‐pyrazol‐5‐yl}‐1‐(2‐triazolethyl‐ β ‐ d ‐glucopyranoside)‐1 H ‐1,2,3‐triazole‐4‐methanamine), regardless of the structural similarity between these two molecules (Fig.…”

The Plant as Metaorganism and Research on Next-Generation Systemic Pesticides – Prospects and Challenges

“…Moreover, lateral transport has been observed in some cases. Nutrient and other carrier systems are usually involved in pesticides transportation across cell membranes and translocation within the plant (Chen et al, 2001; Xia et al, 2014). …”