It's been discontinued for awhile now.
Pretty much studies said it's oral bioavailability is next to nothing, hence why no one makes it anymore. Failed miserably.
Copy/pasta:
Liquid Chromatography-Tandem Mass Spectrometry Determination and Pharmacokinetic Analysis of Amentoflavone and its Conjugated Metabolites in Rats. J Agric Food Chem. 2014 Nov 21;
"Despite these promising activities, the pharmacokinetics of AMF has not been well characterized, beyond establishing its poor oral bioavailability."
"These data collectively suggested that AMF was rapidly conjugated (glucuronidated and/or sulfated) in the bloodstream, which may explain its rapid clearance time and high volume of distribution."
"After a 300 mg/kg PO dose, a low level of the free form of AMF was detected in the bloodstream throughout the analysis period (Figure 4c and Table 5). In contrast, higher concentrations of the AMF conjugates were detected, representing 90.7% of the total AMF, based on the AUC0-t (Table 6). Comparison of the AUC0-t 352 values following PO and IV doses indicated that the absolute oral bioavailability of total AMF was low (~ 0.13% ± 0.04%)."
"Although encouraging efficacy data has been reported for AMF in rats 17,18,there have been no careful analyses of the drug metabolism and pharmacokinetic (DMPK) properties of AMF. Previous analyses of related compounds demonstrated that the biflavonoid glycoside moiety can undergo extensive biotransformation in vivo, 29,31 and that the glucuronide and sulfate conjugates are actually the predominant forms found in the bloodstream, urine, and bile. Hence, it is reasonable to assume that the conjugates are the bioactive forms.30"
"Our preliminary investigations of the biotransformation of AMF after PO dosing in rats revealed that glucuronide, sulfate, and sulfate/glucuronide conjugates predominated over the parent compound in the urine and feces, and an in situ perfused rat intestine-liver model also confirmed this nresult (unpublished data). Thus, like other biflavonoids, the conjugated form of AMF is most likely to be the bioactive form."
"Our study also confirmed that AMF showed very low bioavailability after oral dosing. Although the reasons for this are not entirely clear, it is generally thought that large, highly polar molecules are not absorbed efficiently following oral administration.36,37
Consistent with this hypothesis, the apical transporter multidrug resistance-associated protein 2 (MRP2) can efflux some flavonoids, resulting in a dramatically reduced uptake.9 At any rate, oral administration is clearly not the preferred route for AMF delivery."
pubs.acs.org/doi/pdfplus/10.1021/jf5019615
