Japanese researchers have developed a way to make Tamiflu, the anti-viral drug believed to counter bird flu in humans, without using a scarce botanical ingredient used by Swiss drug maker Roche, news reports said Saturday. Tamiflu uses Shikimic acid derived from the Chinese anise fruit, which is sold dried as a popular spice and medicinal herb. Huge volumes of the plant are needed to produce Shikimic acid, with 30 kilograms of anise pod yielding only 1 kilogram of acid. The fruit is in short supply and can only be harvested between May and March in four Chinese provinces. A research team at the University of Tokyo can now manufacture Tamiflu using the chemical 1,4-cyclohexadiene instead of Shikimic acid, according to reports carried by the Yomiuri Shimbun and Kyodo News agency, which quoted head researcher Masakatsu Shibasaki. The university has applied for a patent on the method, Kyodo said. The university couldn't be reached for comment Saturday.