The white peony, known as Bai Shao in Traditional Chinese Medicine, has reigned for over 1,200 years as an indispensable remedy for gynecological disorders. This root of Paeonia lactiflora, harvested from four- to five-year-old cultivated plants and then dried after its bark has been removed, conceals behind its unassuming appearance a fascinating pharmacology that modern science is only beginning to decipher.
Paeoniflorin: A Powerful Natural Muscle Relaxant
The major active compound in the white peony is called paeoniflorin, a monoterpene glycoside that represents more than 90% of the total glucosides extracted from the root. This compound has a remarkable ability to relax smooth muscles, documented in multiple experimental models. Studies on isolated rat stomach and uterus have demonstrated that paeoniflorin induces dose-dependent muscle relaxation.
More specifically regarding the uterus, research has revealed that paeoniflorin inhibits spontaneous or oxytocin-induced contractions in vitro. A study published in PMC showed that an aqueous extract of peony pollen significantly decreased the number of abdominal spasms, prolonged the latency period, and improved pathological uterine lesions in mice with primary dysmenorrhea. These antispasmodic effects explain the traditional use of Bai Shao to relieve menstrual cramps.
Paeoniflorin also acts as a documented analgesic. Animal studies have confirmed that peony extract suppresses acetic acid-induced contortion reactions, groaning elicited by electrical stimulation, and hot plate reactions in mice and rats, in a dose-dependent manner. Crucially, naloxone does not abolish these effects, proving that analgesia is not mediated by opioid receptors but by a distinct mechanism involving adenosine A1 receptors.
Action on prostaglandins: key to menstrual relief
In the 1970s, scientists discovered why some women suffer from severe menstrual cramps. They produce abnormally high levels of prostaglandin F2 alpha, up to seven times higher than women without dysmenorrhea. This inflammatory molecule causes violent and painful uterine spasms.
Japanese research published in 1996 demonstrated that the Shakuyaku-kanzo-to formula, combining white peony and licorice, inhibits prostaglandin production in the human uterine myometrium. The mechanism involves the inhibition of phospholipase A2, the enzyme responsible for the release of arachidonic acid, a precursor to prostaglandins. Other studies have confirmed the inhibition of arachidonic acid itself, platelet-activating factor, and a reduction in the formation of free radicals.
This anti-prostaglandin action explains why white peony does more than just mask the pain: it addresses the root cause of menstrual cramps by reducing inflammation and excessive uterine contractions.
Clinical evidence: modest but real efficacy.
A double-blind clinical study published in 1997 in the American Journal of Chinese Medicine evaluated the analgesic effect of an herbal formula containing white peony on primary dysmenorrhea. The results showed a significant reduction in the intensity and duration of pain compared to placebo. The effect was greater after two menstrual cycles of use, suggesting a cumulative benefit.
However, the majority of clinical trials have tested the traditional Shakuyaku-kanzo-to (TJ-68) formula combining equal parts peony and licorice, rather than peony alone. A review of clinical studies indicates that this combination effectively relieves primary dysmenorrhea with yin deficiency. In an open-label trial, eleven patients suffering from hot flashes secondary to antihormonal treatment for endometriosis, adenomyoma, or fibroids experienced significant relief, with four achieving complete relief. The synergy with licorice appears to be crucial. Paeoniflorin alone demonstrates antispasmodic activity, but this action is potentiated in vitro and in vivo by the addition of glycyrrhizin, the active compound in licorice. This scientific observation validates the traditional wisdom that rarely prescribes peony alone.
Beyond dysmenorrhea: other gynecological applications
An open-label trial of 11 women suffering from leukorrhea and corpus luteum insufficiency showed that the Toki-shakuyaku-san formula containing peony normalized the menstrual cycle and reduced vaginal discharge. Even more impressively, a study revealed that this formula increased the effectiveness of clomiphene in infertile women, raising the pregnancy rate by 33% compared to clomiphene alone.
White peony also shows potential in polycystic ovary syndrome (PCOS). Trials using the TJ-68 formula demonstrated regulation of the LH/FSH ratio and a decrease in serum testosterone levels, leading to ovulation in seven of the eight women treated. In another study of 20 women diagnosed with PCOS, the formula lowered testosterone in 90% of participants, 25% of whom became pregnant.
The proposed mechanism involves a direct action on the ovary, increasing aromatase activity, which converts testosterone to estradiol, thus reducing serum testosterone levels. Paeoniflorin also appears to inhibit testosterone synthesis in vitro without affecting estradiol synthesis.
Effects on generalized muscle cramps
The muscle-relaxing action of peony is not limited to the uterus. Clinical trials have confirmed the efficacy of Shakuyaku-kanzo-to in relieving muscle cramps due to liver cirrhosis, diabetes, and dialysis. One study demonstrated that the formula significantly reduces cramps in dialysis patients.
This property is explained by the effect of paeoniflorin on skeletal muscle contraction responses. In vitro and in vivo, the compound inhibits muscle contractions, an effect potentiated by the addition of glycyrrhizin. Patients suffering from generalized muscle spasms could therefore benefit from this plant, although studies have primarily focused on gynecological applications.
Dosage and precautions for use
- In Traditional Chinese Medicine, the recommended daily dose of dried white peony root ranges from three to ten grams, usually prepared as a decoction. For liquid extract, the dosage is three to five milliliters, taken once or twice daily. The classic Shakuyaku-kanzo-to formula contains six grams of white peony and six grams of licorice root.
- For standardized paeoniflorin supplements, dosages typically range from 300 to 600 milligrams of standardized extract taken two to three times daily. Clinical studies demonstrating efficacy generally use these dosage ranges for at least two consecutive menstrual cycles.
- Side Effects and Contraindications: White peony has an overall favorable safety profile when used at the recommended doses for periods of up to twelve months. Reported side effects are rare and mild: occasional stomach upset in some sensitive individuals.
- However, several precautions are necessary. Peony has documented anticoagulant properties that may potentiate the effects of anticoagulant or antiplatelet drugs such as warfarin, aspirin, or clopidogrel. Cases of interaction have been reported in the medical literature. Individuals taking anticoagulants or suffering from clotting disorders should avoid this plant.
- White peony is contraindicated during pregnancy because high doses may cause uterine contractions. Women with a history of heavy menstrual bleeding should also exercise caution. Finally, although data remain limited, a possible interaction with drugs metabolized by cytochrome P450 cannot be ruled out.
- Cited scientific sources:
- https://ndnr.com/pain-medicine/peony-for-womens-health-and-beyond/
- https://pmc.ncbi.nlm.nih.gov/articles/PMC3108611/
