Medicinal Plants in Dermatology: Psoralen
Learn about the history, composition, and modern applications of a scientifically proven plant-derived therapy for skin conditions.
Hot off the presses! We have an exciting new publication out from the Quave Lab, published in the Society for Investigative Dermatology open access journal JID Innovations! This was coauthored by a visiting Fulbright scholar in my lab, two undergraduates, one medical student, one dermatology resident, and myself. I love it when such a diverse team comes together on a collaborative writing project like this one!
Abstract: Skin conditions are a common health concern faced by patients of all ages. For thousands of years, plants have been used to treat various skin conditions, including acne, vitiligo, and psoriasis, to name a few. Today, with increasing patient preference for natural therapies, modern medicine is now more than ever incorporating age-old knowledge of herbal remedies useful in treating skin conditions into modern-day treatments. This review covers various plant-derived therapeutics (polyphenon E [sincatechins], psoralen, salicylic acid, anthralin, podophyllotoxin, and Filsuvez [birch triterpenes, oleogel-S10]) that have demonstrated scientific evidence of clinical efficacy for dermatologic disorders. The discovery, composition, history of use, and current uses in dermatology are summarized for each botanical ingredient.
Here is the full article information and you can access the full text at the title hyperlink below:
Israyilova, A., T.V. Peykova, B. Kittleson, P.C. Sprowl, T.O. Mohammed, C.L. Quave. (2025) From Plant to Patient: A Historical Perspective and Review of Selected Medicinal Plants in Dermatology. JID Innovations, 5:1: 100321
There is a lot to unpack in the article, so I thought it might be most helpful for the readership of Nature’s Pharmacy to break it down, plant by plant, in this post and future ones. To start, let’s begin with psoralen.
Discovery and Composition
Psoralen is a natural compound found in plants like figs, celery, parsley, and fennel seeds. It has a history of use dating back to ancient Egypt and India (around 1200 BCE) for treating vitiligo, a condition that causes skin discoloration. Herbalists would boil specific plants, such as Ammi majus or Psoralea corylifolia, to create a remedy that was either applied to the skin or ingested before sun exposure. Modern research identified 8-MOP (8-methoxypsoralen, methoxsalen, also referred to as “psoralen”) as the active ingredient in these treatments, and it is still used in medicine today.
History as a Drug
PUVA therapy, combining psoralen and UVA light, has roots in ancient Egypt (1200 BCE) but was modernized in the 1940s when El Mofty identified methoxsalen for treating vitiligo. By the 1970s, Harvard researchers adapted PUVA for psoriasis using oral methoxsalen and UVA exposure. Today, Oxsoralen Ultra is used for systemic or topical PUVA therapy. Oral doses are taken 75 minutes before treatment, while soak or bath methods involve 30 minutes of soaking, drying, and UVA exposure. PUVA includes clearing and maintenance phases, with sessions tailored to the condition. It also inspired photodynamic therapy for skin cancers and other conditions.
Mode of Action
Psoralens are compounds that absorb UVA light, allowing them to bind to DNA and form cross-links. This process blocks DNA synthesis, which helps treat skin conditions. Initially, PUVA therapy was thought to target skin cells, but research later showed it primarily affects immune cells, reducing inflammation and improving symptoms like psoriasis.
Uses in Dermatology Today
PUVA therapy, FDA-approved for conditions like psoriasis, vitiligo, and cutaneous T-cell lymphoma, works by targeting or destroying disease-causing skin cells. Psoralen is taken orally or applied topically before UVA light exposure. While effective, long-term use can cause freckling, wrinkles, and skin cancer risk, requiring regular skin check-ups.
Psoriasis
Psoriasis is a chronic skin condition caused by an overactive immune system, leading to scaly, itchy patches. PUVA therapy effectively treats severe cases by reducing immune activity and promoting cell death in affected skin. While risks include skin toxicity and cancer, PUVA is beneficial for hard-to-treat psoriasis and darker skin types.
Vitiligo
Vitiligo is an autoimmune disorder causing skin depigmentation. PUVA therapy helps by stimulating melanocyte activity, leading to repigmentation over time. Combining PUVA with treatments like calcipotriol or low-dose azathioprine has shown better results, improving skin repigmentation more effectively than PUVA alone in patients with vitiligo.
Cutaneous T-Cell Lymphoma
Cutaneous T-cell lymphoma (CTCL) is a type of skin cancer caused by abnormal T cells, often appearing as scaly patches or plaques. PUVA therapy is effective for early-stage CTCL but not for tumor stages. It can also be used in photopheresis, where blood is treated with light outside the body to trigger an immune response against cancer cells, slowing disease progression. PUVA also increases certain immune signals, reducing inflammation and helping target diseased cells.
I hope you enjoyed learning a bit about this important plant-derived medicine! As it is Giving Tuesday, I’d be remiss if I didn’t include this pitch for support of my research lab. Philanthropic support is critical to our ability to train scientists and conduct research on plant-derived compounds in our search for nature’s next medicines. You can make a tax-deductible donation directly to my lab at the secure Emory Giving page.
Yours in health, Dr. Quave
Cassandra L. Quave, Ph.D. is a Guggenheim Fellow, CNN Champion for Change, Fellow of the National Academy of Inventors, recipient of The National Academies Award for Excellence in Science Communication, and award-winning author of The Plant Hunter. Her day job is as professor and herbarium curator at Emory University School of Medicine, where she leads a group of research scientists studying medicinal plants to find new life-saving drugs from nature. She hosts the Foodie Pharmacology podcast and writes the Nature’s Pharmacy newsletter to share the science behind natural medicines. To support her effort, consider a paid or founding subscription to Nature’s Pharmacy or donation to her lab research.
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Hi Cassy! I notice that psoralen comes from the same plant species as bakuchiol. The latter is touted as an anti-wrinkle ingredient in lotions and serums. Do you have information on the validity, or not, of those claims for bakuchiol?