A Novel Fluorescence-Based Microplate Assay for High-Throughput Screening of hSULT1As Inhibitors.

Human sulfotransferase 1As (hSULT1As) play a crucial role in the metabolic clearance and detoxification of a diverse range of endogenous and exogenous substances, as well as in the bioactivation of some procarcinogens and promutagens. Pharmacological inhibiting hSULT1As activities may enhance the in vivo effects of most hSULT1As drug substrates and offer protective strategies against the hSULT1As-mediated bioactivation of procarcinogens. To date, a fluorescence-based high-throughput assay for the efficient screening of hSULT1As inhibitors has not yet been reported. In this work, a fluorogenic substrate (HN-241) for hSULT1As was developed through scaffold-seeking and structure-guided molecular optimization. Under physiological conditions, HN-241 could be readily sulfated by hSULT1As to form HN-241 sulfate, which emitted brightly fluorescent signals around 450 nm. HN-241 was then used for establishing a novel fluorescence-based microplate assay, which strongly facilitated the high-throughput screening of hSULT1As inhibitors. Following the screening of an in-house natural product library, several polyphenolic compounds were identified with anti-hSULT1As activity, while pectolinarigenin and hinokiflavone were identified as potent inhibitors against three hSULT1A isozymes. Collectively, a novel fluorescence-based microplate assay was developed for the high-throughput screening and characterization of hSULT1As inhibitors, which offered an efficient and facile approach for identifying potent hSULT1As inhibitors from compound libraries.

Discovery of baicalein derivatives as novel inhibitors against human pancreatic lipase: Structure-activity relationships and inhibitory mechanisms.

Human pancreatic lipase (hPL) is a vital digestive enzyme responsible for breaking down dietary fats in humans, inhibiting hPL is a feasible strategy for preventing and treating obesity. This study aims to investigate the structure-activity relationships (SARs) of flavonoids as hPL inhibitors, and to find potent hPL inhibitors from natural and synthetic flavonoids. In this work, the anti-hPL effects of forty-nine structurally diverse naturally occurring flavonoids were assessed and the SARs were summarized. The results demonstrated that the pyrogallol group on the A ring was a key moiety for hPL inhibition. Subsequently, a series of baicalein derivatives were synthesized, while 4'-amino baicalein (ABA) and 4'-pyrrolidine baicalein (PBA) were identified as novel potent hPL inhibitors (IC50 < 1 µM). Further investigations showed that scutellarein, ABA and PBA potently inhibited hPL in a non-competitive manner (Ki < 1 µM). Among all tested flavonoids, PBA showed the most potent anti-hPL effect in vitro, while this agent also exhibited favorable safety profiles, unique tissue distribution (high exposure level to intestinal system but low exposure levels to deep organs) and impressive in vivo effects for lowering blood triglyceride levels in mice. Collectively, this work uncovers the SARs of flavonoids against hPL, while a newly synthetic flavonoid (PBA) emerges as a potent hPL inhibitor with favorable safety profiles and impressive anti-hPL effects in vivo.