The ginkgo tree is a living fossil, dating back at least 270 million years. So, it’s no surprise to find uses for the plant show up in various texts and writings of antiquity. For instance, traditional Chinese medicine is riddled with concoctions and tinctures that blend herbal elements together and often have some real medicinal value. The antimalarial artemisinin is a recent example where ancient Chinese healers would create an elixir from the wormwood plant that had some effectiveness at treating fevers that resembled those from malaria. Dr. Youyou Tu had the forethought to scan these ancient texts searching for more effective malaria treatments. Her intuition paid off and led her to receive the Nobel Prize in 2015.
Now, while examining a nearly 200-year-old copy of a 16th-century text on traditional Chinese medicine—called the Ben Cao Gang Mu—for inspiration, investigators at Emory University found that extracts from the seeds of the Ginkgo biloba tree showed antibacterial activity on pathogens that can cause skin infections such as acne, psoriasis, dermatitis, and eczema. Findings from the new study were published recently in Frontiers in Microbiology through an article titled “Validation of a 16th Century Traditional Chinese Medicine Use of Ginkgo biloba as a Topical Antimicrobial.”
“It was like blowing the dust off knowledge from the past and rediscovering something that had been there all along,” explained lead study investigator Xinyi (Xena) Huang, an undergraduate biology major at Emory who studied the text as part of her senior thesis project. She has since graduated from Emory and is now a student at the University of Maryland School of Pharmacy.
“To the best of our knowledge, this is the first study to demonstrate the antibacterial activity of ginkgo seeds on skin pathogens,” added senior study investigator Cassandra Quave, PhD, assistant professor at Emory’s Center for the Study of Human Health and the School of Medicine’s department of dermatology. “This paper is just one more example of how much we still have to learn about the pharmacological potential of the complex chemistry of plants.”
In the current study, the researchers identified the main compound that was likely responsible for the antibacterial activity, ginkgolic acid C15:1. Unfortunately, in its concentrated form, this compound has been demonstrated to have skin toxicity, so there are still many hurdles to overcome before ginkgo seed extracts could be considered for use in a modern-day medical context.
“One possible strategy in the search for new antibiotics would be to investigate ways to modify the structure of the particular ginkgolic acid tied to the antibacterial activity, to try to improve its efficacy and also to reduce its toxicity to human skin cells,” noted co-lead study investigator François Chassagne, PharmD, PhD, a researcher in the Quave lab.
Modern-day researchers have studied ginkgo extensively in search of medical benefits for everything from memory enhancement to macular degeneration, but there is still “no conclusive evidence that ginkgo is helpful for any health condition,” according to the web page of the National Institutes of Health’s National Center for Complementary and Integrative Health. Yet, most previous studies have focused on the ginkgo leaves.
When walking across campus, pondering what to focus on for her senior thesis, a ginkgo tree caught Huang’s eye. She knew that the tree was used in traditional Chinese medicine, although she did not know any details, so she decided to research it.
Huang’s interest grew when she learned that Emory had an 1826 version of the Ben Cao Gang Mu, or Compendium of Materia Medica. Considered the most comprehensive book on traditional Chinese medicine, it was compiled and written in the 16th century by Li Shi-Zhen during the heyday of the Ming Dynasty. The original compendium is vast, encompassing dozens of volumes, but Huang had only seen greatly condensed versions that are sold in Chinese bookstores.
Huang never imagined she would be touching such an old copy of the Ben Cao Gang Mu. “You can feel the history in it,” she says. “The paper is so yellow, thin, and fragile that I was afraid I would break the pages as I was turning them.”
A volume labeled “Grains, Vegetables, Fruits” described 17 traditional uses for the ginkgo seed, including eight for skin disorders such as chapped hands and feet, rosacea, crab louse-induced itchiness, dog-bite wound abscesses, and pustules. Li Shi-Zhen recommended preparing a paste of ground up seeds mixed with rice wine or other alcohol, or by immersing the crushed seeds in rapeseed oil. The paste could then be applied to the affected area.
Interestingly, a previous study found that ginkgo seed coats demonstrated antibacterial activity against some intestinal bacterial pathogens. And ginkgo leaves have shown antibacterial activity on both some intestinal bacteria and on the skin pathogen S. aureus.
Huang, however, wanted to test the information she had gleaned from the ancient text for the use of ginkgo seeds as a topical treatment for skin disorders. Skin pathogens are of particular interest to the Quave lab, which focuses on finding new approaches to treat antibiotic-resistant bacteria. Huang gathered ginkgo samples for testing. Extractions from the seeds were processed as closely as possible to the recommendations of the Ben Cao Gang Mu, using either water, ethanol, or rapeseed oil. Huang and Chassagne conducted microbial experiments—including the evaluation of ginkgo extracts from the seed nut, immature seeds, and the seed coat—on 12 different bacterial strains.
Amazingly, the results showed that the ginkgo seed coats and the immature seeds exhibited antibacterial activity on three of the strains tested: C. acnes, S. aureus, and S. pyogenes. Statistical analysis also found a positive correlation between the antimicrobial activity of the ginkgo samples and the concentration of ginkgolic acid C15:1, suggesting it was involved in the activity.
“Our finding is still in a basic, benchtop phase—these extracts have not yet been tested in animal or human studies—but it is still a thrill for me to learn that this ancient story in the Ben Cao Gang Mu appears to be real,” Huang concluded. “As a student pharmacist, this gives me more appreciation for the value of using ancient plant remedies to guide modern-day research.”