Cattle appear to be more sensitive to the phototoxicity of hypericin than sheep. In one test with cattle, a single dose of 1 g per kg bodyweight of dried Hypericum showed no photosensitization or changes in liver enzymes, but 3-4 g did. If humans were as sensitive to hypericin as cattle, this dose would correlate to 59 gms for a 130 lb individual. Importantly, hypericin does not seem to be accumulative. (118)

Although there have been a considerable number of studies published demonstrating the phototoxicity of hypericin in various animal species (119, 120), a thorough search by this writer brings to light no evidence that there has ever been a case involving human toxicity.

Some authors recommend caution when using large quantities of St. John's wort extract for medicinal uses, particularly for people with fair skins, who should not expose themselves to strong sunlight during Hypericum therapy (121). Judging by the available literature, a very moderate dose, up to 4 g of the dried herb, 30 ml of the 1:5 tincture (40% EtOH), or 240 grams of the 1:5 powdered extract per day (standardized to 0.125% hypericin), should not pose a problem, if sunlight restriction is followed (122, 123), especially given the widespread use of H. perforatum extracts in Europe. One major product is recommended by the manufacturer to be taken as 40 mg tablets (1-2 tablets, 3 times a day).

Preparations
Hypericin was more effectively extracted with glycol and sunflower seed oil when the moisture content of the herb was between 50 and 70%, and 2-7 times higher at 70 degree C. than at 20 degree C. The menstruum was saturated after 12 hours and 24 hours respectively, but it took 3-4 extractions to exhaust the herb (124). The total extraction in one hour of hypericin with ethanol was not dependent on water content of the herb. The authors conclude that ethanol is the most suited menstruum for the extraction of dried material (125).

Freshly air-dried herb was moistened to 70-72% moisture and extracted at 70 degree at 1:7 with sunflower seed oil. The total content of hypericin was 2.5 mg%, and extracting the marc with ethanol could increase the content to 3.32 mg% (a 25% increase)(126).

Hypericin content of a juice of H. perforatum and a powdered extract dropped by 14% during 1 year, and the dry extract remained stable, when stored at 20 degree C. When stored at 60 degree C., the hypericin content dropped 33%, 33%, and 47% from a powdered extract, tablets, and liquid juice, respectively (127).

In one extensive study, up to 80% of the hypericin was destroyed by drying of the fresh plant in sunlight (128). For this reason, modern herbalists generally grind the fresh tops of Hypericum and immediately macerate them in olive oil or sunflower seed oil. The oil is then pressed and filtered after two weeks, and should be stored in amber bottles away from heat and light. An alcoholic tincture is made in the same way, macerating the fresh, ground tops in 70% ethyl alcohol and 30% distilled water.

St. John's wort is currently official in the pharmacopeias of Czeckoslovakia, Poland, Roumania, and Soviet Union (129).

Identification and Adulteration
For identification of cut and sifted material from the commercial drug market, note the two opposite ridges on the stems. These are prominent, and an important character in differentiating different Hypericum species (see Fig. 1).