Pharmaceutical interest

Inhibition of Cytochrome P450 : To date, the therapeutic potential of Humulus scandens (Lour.) Merr. remains unexplored. A number of flavonoids isolated from Humulus lupulus L. (hop), inhibit potently and selectively the human cytochrome P450 which is responsible for steroid metabolism and microsomal oxidative

Fig. 48. Humulus scandens (Lour.) Merr. From: KLU Herbarium 042729. Field collector & botanical identification: Luo Lin-bo, 20 Aug 1994.Geographical localization: Hunan, China, XiningCo., 26° 4' North-110° 8' East, altitude: 320 m.

system (Henderson MC et a/., 2000). Such flavonoids could be responsible for the possible diuretic, hormonal and anti-malignant properties of Humulus scandens (Lour.) Merr. Cytochrome P450 is involved in the electron transport necessary for the 11-hydroxylation of cholesterol into aldosterone which is a steroid hormone that inhibits urination. Metapyrone is an example of a diuretic drug which acts by inhibiting 11-hydroxylation of the steroid nucleus. Three flavonoids, xanthohumol, dehydrocycloxanthohumol and isoxanthohu-mol, isolated from hop inhibit dose dependently (0.1 ^M-100 ^M) the proliferation of human breast cancer (MCF-7), colon cancer (HT-29) and ovarian cancer (A-2780) cultured in vitro (Miranda CL et al, 1999). It will be interesting to learn whether a more intensive future research on Humulus scandens (Lour.) Merr. will disclose any molecules of chemotherapeutic interest.

Hops is well-known to be estrogenic owing to the phytoestrogens 8-prenylnaringenin (8-isopentenylnaringenin) which binds to estrogen receptors (Milligan SR et al., 2000). One might set the hypothesis that an estrogenic mechanism would explain the use of Humulus scandens (Lour.) Merr. to invigorate the genital system and to impede spermatorrhea. Estrogens act on the hypothalamus to inhibit the release of FSH which stimulates spermatoge-nesis. In addition, estrogen also inhibits the release of ICSH (LH), thereby decreasing testosterone production and inhibiting libido.

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