Scientists in Yunnan unlock secrets of 'magical' microbe-killing plant
Pleasant-tasting relative of Sichuan pepper, long known to tribal doctors, shows promise as a safe, effective killer of dangerous microbes
Scientists say they have discovered that the pepper-like fruit of a plant native to Yunnan can kill germs as efficiently as antibiotics, with few side effects.
Tribal doctors have used oil extracted from the seeds to cure stomach disorders and flesh wounds since ancient times. The mild flavoured fruit has a pleasant fragrance and is used as a food preservative.
The herbal germ-killer shows promise in treating patients while avoiding the serious overuse of antibiotics in China, according to researchers at the Chinese Academy of Sciences.
Dr Zhang Ping, a researcher at the internationally acclaimed CAS Xishuangbanna Tropical Botanical Garden in Mengla county and an author of a study on the plant, said that due to the region’s isolation, the “magical power” of ma qian was known to few people outside the local Dai population.
“I had never heard of it until I came to Xishuangbanna,” Zhang said. “It is totally new to the rest of China and the world.”
After witnessing the herb’s “incredible” effects on patients, Zhang and her colleagues analysed the plant using modern methods and equipment. They hope to begin production of a medicine but must first study the plant in more detail and consider how to cultivate it on a large scale, she said.
Ma qian, known by botanists as Zanthoxylum myriacanthum Wall ex Hook f. var. pubescens Huang, is a leafy shrub from the genus Zanthoxylum, which includes more than 250 species including two that produce the famous Sichuan pepper, or hua jiao.
Yunnan ma qian is not to be confused with the similarly sounding but completely different plant ma qian zi, or Strychnos nux vomica,which is found widely in southern China, including Hong Kong. The seeds of the latter are used, not without controversy, in traditional Chinese medicine as a painkiller. Yunnan ma qian belongs to the plant order Rutales, which includes lemons, oranges and other citrus plants. Toxic ma qian zi belongs to the order Gentianales.
The study confirmed the plant’s potential as an effective alternative to conventional antibiotics. The ma qian fruits not only wiped out most common pathogens and spoilage organisms, but reduced inflammatory symptoms with no known negative effects on cells.
Zhang and her team published their paper in the latest issue of the Journal of Ethnopharmacology, an international academic journal, last month.
China is the world’s largest producer and consumer of antibiotics. Per-head consumption was 138 grams of the drug per year, 10 times the average in the United States, in 2012, according to the health commission.
Overuse of antibiotics not only causes side effects in patients but accelerates immunity to diseases. For instance, nearly 7 per cent of tuberculosis cases on the mainland are resistant to a variety of drugs, compared with about 2 per cent in Western countries.
Ma qian’s germ-killing capability might come from the complex chemical composition of its fruit, including limonene, which constitutes nearly 70 per cent of the essential oil.
The compound, with its distinct citrus odour, is a known antimicrobial agent, but this alone probably does not fully explain the outstanding performance of ma qian oil, suggesting the presence of other chemical compounds whose effects have not been thoroughly determined, Zhang said.
The anti-inflammatory ability of ma qian was most apparent at a concentration of 40 micromoles per litre, a level at which it eliminated harmful waste nitric oxide produced by cells as they fought off invading bacteria.
“We are preparing clinical trials of the application to turn the plant into a medicine,” Zhang said.
“We still need to know more about the plant before progressing to mass applications. Tribal doctors might have used it for thousands of years, but to modern science it is a completely new substance and many questions remain unanswered.”
Some compounds in the fruit remained unidentified and Zhang’s team had to determine their nature and role in killing pathogens.
The prefectural government of Xishuangbanna had tried earlier to sell ma qian to other regions but could find no buyers due to a lack of knowledge about its use.
Local people cultivated the plant in fields on a small scale, which was not suitable for mass production of modern drugs, Zhang added.
Yunnan is China’s most geographically and culturally diverse province, with microclimates ranging from tropical to high alpine. Xishuangbanna has the highest level of biodiversity in the country. Many plants in its remote areas remained unstudied, even undiscovered, and there was a high chance that many more had potential benefits to society, Zhang said.
Several other plants have been studied as alternatives to antibiotics. Andrographis paniculata, a common tropical herb found throughout Asia and called chuan xin luan in China, has been found to be an effective germ killer in laboratory tests.
Despite advances in science, modern medicine remains highly reliant on the plant kingdom. One in four modern drugs are derived from plants, yet only 0.5 per cent of the world’s known plants have been studied in depth by modern science for their medicinal properties.
