I think amentoflavone is a great ingredient to supplement with. You should check out Powermax XT if you're interested, it contains 100mg of Selaginella tamariscina, which is 90% amentoflavone. I find it helpful for improving blood flow and muscle contraction, increasing pumps, and helping with mood and alertness.
Powermax XT also provides you with a variety of other great staple supplements, which makes it an easy go-to daily supplement that will provide quality amento
Pretty much studies said it's oral bioavailability is next to nothing, hence why no one makes it anymore. Failed miserably.
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parent compound in the urine and feces, and an in situ perfused rat intestine-liver model also confirmed this nresult (unpublished data).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."
Pretty much, yup. According to every bit of science, it does nothing (BCS Class IV using Caco-2)
Biopharmaceutics Classification System Class IV - low permeability, low solubility
These compounds have poor bioavailability. Usually they are not well absorbed over the intestinal mucosa and a high variability is expected.
The considerable impact of the Caco-2 cell monolayer model can be measured in at least two ways. First, considering that poor pharmacokinetic properties accounted for ~40% of drug failures in development in the early 1990s and only ~10% by 2009, an interval in which Caco-2 monolayers were widely used throughout the pharmaceutical industry to predict absorption, it is not unreasonable to attribute some of that shift to this simple yet powerful model. Second, the 1989 Gastroenterology paper that demonstrated the utility of the model for this application has been cited more than 1000 times since its publication.