Several times a year, Chris Kilham ventures into the Amazonian jungles where he gets together with shamans for a few drinks. These are occasions that make a big Friday night in Lan Kwai Fong seem like a stroll through Victoria Park.
The Amazonian tipple of choice is ayahuasca, which Kilham describes as a "profoundly potent psychoactive plant brew". Made from a pounded mixture of the ayahuasca ( Banisteriopsis caapi) vine and the leaves of Psychotria viridis, the drink is rich in the hallucinogenic compound DMT and has long been used to induce spiritual visions. It has also proved useful for dealing with a range of conditions from fatigue and stomach problems to depression and psychological trauma.
"It's very powerful, and you spend all night having these wild visions while the shamans sing healing songs," Kilham says. "It's pretty out there, but it's actually medicine."
Such experiences are all in a day's work for the 61-year-old American, who has built up a global reputation as a medicine hunter over the past 30 years. Working on behalf of clients such as French botanical extraction giant Naturex and US-based supplement makers, Kilham has travelled to more than 30 countries to identify and establish trade in medicinal plants.
Invariably, he immerses himself in the local culture - whether that means joining firewalk rituals or getting high with shamans.
"If the way to get in with these healers, who know the use of hundreds of plants, is to sit in this ritual and drink this medicine with them, I'm going to do that," says Kilham, who was in Hong Kong last month for a natural foods expo. "It has been personally rewarding and also very good for my work."
In Vanuatu, which he visited annually for six years in the '90s, Kilham wound up firewalking with tribesmen from Baie Martellie village. "I was always scared, but it was a remarkable experience. Of course, in doing that with the native people, it totally solidified our friendship."
Kilham, then working as a herb expert, believes his close relationship with the village chief helped his work in exploring the benefits of kava, a plant with stress-relieving properties.
Pacific island cultures have consumed a beverage made from pounded kava root and hibiscus for about 3,000 years as a social drink. Thanks largely to Kilham, who collaborated with a US-based company to develop kava as an alternative treatment for anxiety and related conditions, it entered public consciousness in the West.
"It caught on like wildfire," he says. There was "this big flashbomb of media. And then overnight I was kind of known for doing this work."
That was in 1995. Over the next four to five years he travelled the world at a furious pace, tracking down traditional herbs and helping to develop them. "My actual body of work [eventually] caught up with my reputation," he says.
It has turned into a dream job for Kilham, and allowed him to combine two passions he discovered in his teens - herbs and travel.
Kilham now serves as Fox News' Medicine Hunter, appearing online and on television channels. He is also a frequent guest on popular US TV programme The Dr Oz show and has written 14 books and many publications on medicinal plants, natural products and yoga.
Despite having only an undergraduate degree in holistic health and no formal training in botany, Kilham has taught ethnobotany - his title is explorer-in-residence - at his alma mater, the University of Massachusetts Amherst, since 2000.
The New York Times called him "part David Attenborough, part Indiana Jones". But Kilham stresses that he doesn't discover anything new; he simply bridges indigenous knowledge and practices with the mass market.
In China, for example, he has investigated plants such as Rhodiola rosea (sometimes called rose root or golden root), schizandra (also known as wu wei zi) and goji or wolfberry - plants that have been known for their medicinal properties in this part of the world for centuries, but are relatively unknown in the West.
Kilham says Erigeron breviscapus, a herb native to the southwestern province of Yunnan and known as duan ting fei peng in Chinese and Lifeflower in English, is one of the most exciting that he has researched "because it can save lives". The herb is now made into tablets, capsules and an injectable form, and is used to treat stroke patients, he says.
He concedes there have been concerns over the safety and long-term effects of some herbal formulations, and consumers often find it difficult to tell fad from fact.
Some companies will take the high road - use high quality ingredients, put in effective doses and conduct proper tests - but not everyone does the right thing, Kilham says. It's hard for people to know who to trust, but in many US natural foods stores staff are usually able to recommend reliable brands.
His current project has taken him to Namibia in search of sustainable cultivation of devil's claw root, a plant used in African folk medicine as a digestive tonic, to treat blood disorders, to reduce fevers and as an analgesic.
Hunting native herbs in some of the most remote parts of the world is not without its dangers. On his first trip to Vanuatu, Kilham and a few natives found themselves stranded in a small boat in an extremely rough sea. "We were quite convinced that we were all dead men," Kilham recalls.
They told each other stories and jokes to help ease their fears; the group eventually arrived at their destination cold and shivering and resolved never again to do "such a stupid thing".
Despite the dangers and challenges, Kilham remains passionate about his work. He says he is motivated by three factors: to bring more safe, effective and natural medicines to the public; to promote organic cultivation and sustainable wild harvesting of medicinal plants; and to work with indigenous people and provide them with ethical wages and shared benefits.
Robust growth in demand for alternative medicines has certainly helped Kilham's cause. A report published by Global Industry Analysts last year forecast that the traditional medicine market would swell to US$114 billion worldwide by 2015 as more people seek nature-based products to complement modern medicine.
A voracious reader and a brilliant networker, Kilham usually gets tip offs about promising plants, oils or extracts through research studies or contacts before seeking out clients to collaborate with.
For example, he first learned about maca root in 1995 through a friend in the herbal business. A staple food in the Andes for more than 2,000 years, the turnip-shaped vegetable is said to aid mental clarity and even enhance libido. Kilham approached PureWorld, a company he was working for at that time but was eventually bought out by Naturex. It took three years before the company finally showed an interest and agreed to fund his expedition to Peru.
At new destinations, Kilham usually gets in touch with a trader of a plant. He spends one to three weeks staying with the native community, learning about how the plant is cultivated and turned into the final product. He meets all the people involved in the process and considers if the plant can be commercially viable - whether there is enough of it, whether it can be harvested in a sustainable way and can be easily transported to the city.
Maca turned out to be a win-win for both the Peruvian maca growers and Kilham. Its popularity in the market as a so-called superfood led to a thriving business for the growers, whose standard of living has greatly improved since 1998. Revenues from Naturex's maca business have funded an internet cafe and dental office for the community.
Kilham's success is no doubt due to his unique combination of skills - the ability to not only do good field work, but also the savvy to use the media to his advantage. But his greatest asset is perhaps his knack for getting people to warm up to him quickly. It's no easy task to get indigenous people to share their medicine secrets with outsiders, much less to an American with a commercial interest.
"I show up with tremendous respect," says Kilham. "If everybody is running around barefoot in drawstring shorts and going fishing, I'm barefoot, I'm in drawstring shorts and I'm going fishing with you.
"I want to let people know that I'm not the big American coming in like I'm some sort of special hot shot. What I've found is that if I'm friendly and respectful, and treat people with dignity, they almost always very quickly warm up. That has got me far."