i was reading that i found interesting (not directly concern HepC but a lot of interested point about CYP 3A4)
for exemple

Other Herbals: CYP2D6 and CYP3A4 Activity
Other CYP3A4 inhibitors include Chamomile extracts and tea39, Serenoa repens (Saw palmetto)40, as well as other herbals and spices such as sage, thyme, cloves, the soybean components daidzein and genistein41, pergamottin (active component of grapefruit juice) and glabridin42 (active component of licorice extracts and teas). ]

http://home.earthlink.net/~ckaniklidis/interactions.htm#DrugHerb

well searching about i found some studies about soy (it’s also about ginseng but that was not the related topic

https://www.ncbi.nlm.nih.gov/pubmed/12817527

To determine if soy extract or Panax ginseng increases the urinary excretion of the 6-β-hydroxycortisol/cortisol ratio as a marker of cytochrome P450 (CYP) 3A enzyme induction, subjects received a soy extract containing 50 mg isoflavones twice daily (n = 20) or Panax ginseng 100 mg standardized to 4% ginsenosides twice daily (n = 20) for 14 days. Neither Panax ginseng nor soy extract significantly altered the urinary 6-β-OH-cortisol/cortisol ratio, suggesting that unlike St. John’s wort, they are not CYP3A inducers. Studies in vitro using human liver microsomes were performed to determine the effect of soy extract on probe substrates of CYP and UDP glucuronosyltransferase (UGT). Unhydrolyzed soy extract produced very little inhibition of CYP1A2, CYP2A6, and CYP2D6 and a trend of activation of CYP3A4. Hydrolyzed soy extract showed inhibition of all of the CYPs tested, particularly CYP2C9 and CYP3A4. UGT2B15 was the only UGT significantly inhibited. Even though both soy extract and ginseng have been shown to activate CYP3A4 in vitro, there is a lack of an in vitro correlation with the in vivo effects.

then

http://medicinalplants.us/herb-drug-interactions-soya

About Soy fermented natto ( different from miso ..)

Experimental evidence
Experiments in animals to investigate the clinical observations for natto found that natto strongly antagonised the effects of warfarin.In one in vitro metabolism study in human liver microsomes,hydrolysed soya extract inhibited all of the cytochrome P450 isoenzymes tested, particularly CYP2C9 and CYP3A4 (which are responsible for the metabolism of warfarin). This suggests that an increased warfarin effect might have been expected, but the authors point out there is a lack of concordance between in vitro and in vivo findings.