For centuries, the sturdy branches of ข่อย (Khoi)—scientifically known as Streblus asper—have woven through the everyday lives and healing traditions of Thailand and its Asian neighbors. Revered in traditional medicine, immortalized in local folklore, and even etched into the chronicles of early Siamese literacy, this unassuming “toothbrush tree” continues to captivate the attention of healers and scientists alike. Today, the resurgence of interest in natural health remedies repositions Khoi not just as an artifact of folk heritage, but as a candidate for contemporary herbal medicine, demanding a closer look at the science behind its storied reputation.
From remote village lanes in Isan, where elders once crafted toothbrushes from its fibrous twigs, to the ornate temple murals of Ayutthaya depicting children chewing Khoi bark, the tree’s influence is unmistakable. Its wood, bitter yet aromatic, has long been valued for personal care and healing. But what does modern research say about the efficacy and safety of this ancient remedy—and can Khoi still claim a meaningful place in 21st-century Thai health?
Khoi (Streblus asper) is indigenous to Southeast Asia, thriving in the drier climates of Thailand, Cambodia, and neighboring countries. Locally, it carries a tapestry of names—กักไม้ฝอย, ส้มพอ, ซะโยเส่, ขันตา—each echoing regional dialects and mythologies. The plant features in traditional Thai and Ayurvedic pharmacopeias for diverse complaints: toothache, fever, diarrhea, skin diseases, and even as a remedy for more severe afflictions like leprosy, elephantiasis, and cancer (NCBI; WisdomLib). Elderly villagers recall how every part of Khoi—roots, bark, leaves, and latex—has played a role in the medicine cabinets of old.
But Khoi’s importance is more than medicinal; it is cultural. Before the broad adoption of modern paper, schoolchildren in Siam fashioned “Khoi bark paper”—a resilient, parchment-like surface that preserved Buddhist manuscripts and royal decrees for generations (Wikipedia). The tree’s indelible connection to literacy, ritual, and healthcare imparts it with a significance that extends far beyond its botanical form.
So, what does contemporary science reveal about Khoi’s oft-touted healing powers? A deep dive into recent laboratory and clinical studies provides intriguing, if still preliminary, validation for many of its traditional applications. Modern analyses uncover an abundance of bioactive compounds housed within Streblus asper—most notably, a family of molecules called cardiac glycosides, as well as tannins, flavonoids, and saponins. These substances are responsible for a range of pharmacological activities that align impressively with folk uses (PMC; ResearchGate).
A 2024 study isolated ten novel cardiac glycosides from Khoi roots, noting their potential in antiviral therapies—an exciting prospect as the scientific world hunts for plant-derived solutions in an age of resistant pathogens (PubMed). Experimental work has also focused on Khoi’s anti-inflammatory and antimicrobial effects. One notable investigation conducted in Thailand demonstrated that ethanolic extracts of Streblus asper leaves significantly reduced inflammation in rat models, providing a pharmacological explanation for Khoi’s folk use against swollen gums, abscesses, and arthritic pain (ScienceDirect; PubMed). Additional research has highlighted its efficacy against oral pathogens, lending credence to its enduring reputation as a natural “toothbrush” (JDAT PDF).
In fact, Khoi twigs are still popular for dental care in certain Thai communities, giving rise to a niche in the burgeoning market for natural oral hygiene products. Laboratory studies comparing Streblus asper extract to commercial mouthwashes have found that it can reduce plaque, inhibit the growth of cavity-causing bacteria, and promote oral health overall. These findings resonate with the observations of rural health volunteers from the Central Plains, who have long promoted chewing Khoi wood to strengthen teeth and freshen breath (WJPMR).
Beyond its role in dental care, Streblus asper displays a broad spectrum of pharmacological effects. Antioxidant and antidiabetic activities have been demonstrated in laboratory assays, with extracts of the bark and leaves showing promise in lowering blood sugar and combating oxidative stress—a factor linked to aging and chronic disease (NCBI; SciELO). Research out of India and Southeast Asia describes the use of Khoi preparations as an antidiarrheal and anti-dysenteric remedy, as well as an adjunct in the treatment of skin infections due to its antibacterial and wound-healing properties (PubMed).
A 2021 analysis shed light on the cytotoxic and apoptosis-inducing properties of certain cardiac glycosides found in Khoi’s root extracts, showing promise in the laboratory for cancer treatment—though much more work is needed to establish safety and efficacy in humans (PubMed). At the same time, scientists stress that not all components are benign: the very molecules that give Khoi its pharmacological punch, such as cardiac glycosides, must be approached with caution due to their potential toxicity, especially if consumed in large amounts or without professional oversight (ScienceDirect; IJRDPL).
Such caution is, in fact, a recurring theme among researchers. While laboratory and animal studies support many of Khoi’s reputed health benefits, robust clinical data in humans remains limited. Studies examining oral use for dental health provide encouraging evidence, but no major randomized controlled trials have confirmed the effectiveness of Khoi-based products for more serious medical conditions. Reports of acute toxicity in folk medicine are rare, yet data suggests caution, especially for vulnerable groups such as children, pregnant women, and those with underlying heart problems.
From a public health standpoint, the legal and regulatory status of Streblus asper falls under the purview of Thailand’s Ministry of Public Health, which supports research and safe integration of traditional remedies but warns against unsupervised self-treatment. This echoes classic Thai wisdom, where traditional practitioners tailored treatments to the individual, taking into account constitution, age, and existing health issues—a nuanced approach that modern users should emulate by consulting qualified professionals before incorporating Khoi into their wellness routines (MSN News).
The rich folklore surrounding Khoi not only includes its medicinal properties but also cultural rituals. In Northern Thailand, slender Khoi branches are sometimes woven into protective amulets in the belief that their antimicrobial essence guards against evil spirits and disease. During traditional ceremonies, the bark may be ritually offered, symbolizing the hope for community well-being—practices that resonate to this day in rural festivals.
What does the future hold for this time-honored tree? The convergence of ancient wisdom and the latest phytopharmaceutical research suggests that Khoi’s second act is just beginning. With global attention on sustainable and locally sourced remedies, Streblus asper stands poised for further study and safer, evidence-based application. Scientists continue to explore its antiviral, anticancer, and innovative oral health potentials, while environmentalists advocate for the preservation of native Khoi stands as both a genetic resource and a living piece of Thai heritage (SciELO; Phytojournal PDF).
For Thai readers eager to blend tradition with science in pursuing personal or family wellness, Khoi reminds us of the importance of balance. While incorporating traditional herbal wisdom can enrich daily life, all medicinal plants—no matter how venerable—must be approached with respect, careful sourcing, and the guidance of healthcare practitioners. Those interested in exploring Khoi for oral health might look for standardized products or seek advice at a traditional Thai medicine clinic, especially those affiliated with public hospitals participating in government-supervised herbal research pilots.
In conclusion, the enduring legacy of Streblus asper captures the spirit of Thai healing—a seamless thread connecting ancestral lore to the promises of modern medicine. To truly benefit from its gifts, trust not only in tradition but in the wisdom of combining it with rigorous contemporary science. Always consult a licensed medical or traditional health professional before using any herbal product, and remain mindful that what is old can indeed become new again—when illuminated by study, respect, and a readiness to learn.
Sources: Wikipedia, NCBI, PMC, ScienceDirect, WisdomLib, JDAT PDF, ResearchGate, SciELO, MSN News, NCBI, WJPMR, Phytojournal PDF, IJRDPL