You're probably thinking of Milk Thistle. There's been some evidence that it can intefere with bioavailability of PH's, but I don't think it's conclusive. I just recently started taking ~1g of MT just before bed, since my last PH dose is earlier in the day. One thing I unexpectedly have noticed is I'm sleeping like a damn log with that stuff. Not sure if that's a known effect or not, but I haven't slept this well in months!!