Pre-ADMET studies of 5-(3',4'-dihydroxyphenyl)-γ-valerolactone, the bioactive intestinal metabolite of proanthocyanidins

5-(3',4'-Dihydroxyphenyl)-γ-valerolactone (VL) is a bioactive metabolite resulting from the gut microbial metabolism of proanthocyanidins and flavonoids, known for its health-promoting effects, including antidiabetic and anti-inflammatory activities. Although VL has been observed in different in vivo studies, its pre-absorption, distribution, metabolism, excretion, toxicity (ADMET) properties have rarely been investigated. This study aims to address this gap by evaluating the pre-ADMET properties of VL for the first time. Also, the understanding of these properties is significant for correlating the encountered activities to this metabolite. In vitro absorption studies revealed that VL is rapidly metabolized and absorbed as its sulfate phase II conjugate (valerolactone sulfate), which enters systemic circulation and mildly activates the Breast Cancer Resistance Protein efflux transporter. In human S9 liver fraction, a mixture of liver enzymes used to simulate in vivo liver metabolism, VL is metabolized into glucuronic phase II conjugates (valerolactone glucuronide 1 [VLG1] and 2 [VLG2]) with a half-life of 8.72 min and an 80% conversion rate. In human liver microsomes, VL is metabolized at a slower rate (half-life of 23.08 min), suggesting that oxidative metabolism is secondary. Additionally, VL did not activate the pregnane X receptor or inhibit Cytochrome P3A4 (CYP3A4) and Cytochrome P1A2 (CYP1A2) enzymes, indicating no risk of herb-drug interactions with coadministered prescription drugs.