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Khella Extract

Also known as: Khella, Bishop's weed, toothpick weed, khellin, visnagin, Ammi visnaga

Overview

Khella extract is derived from the dried fruits and seeds of *Ammi visnaga*, a plant indigenous to the Mediterranean region. This herbal extract is rich in bioactive furanochromones, primarily khellin and visnagin, which are responsible for its therapeutic effects. Traditionally, Khella has been utilized for various ailments, including kidney stones (urolithiasis), skin conditions like vitiligo and psoriasis, and respiratory issues such as asthma. Modern research is exploring its potential as an antiviral agent, a vasodilator, and a bronchodilator. Its key characteristics stem from its ability to act as a calcium channel blocker, leading to smooth muscle relaxation and vasodilation. It also exhibits antimicrobial and antiviral properties. While there are several clinical and preclinical studies, high-quality randomized controlled trials (RCTs) and meta-analyses are limited, indicating a moderate level of research maturity. The available evidence primarily consists of small clinical trials, animal studies, and in vitro experiments.

Benefits

Khella extract offers several evidence-based benefits, though the strength of evidence varies. For vitiligo, topical khellin combined with 308-nm excimer lamp phototherapy has shown promising results, with small open-label and controlled studies reporting repigmentation in approximately 45-56% of patients, some achieving good to excellent responses. This makes it a potential option for patients resistant to conventional vitiligo therapies. In urolithiasis, Khella extract has demonstrated diuretic effects in animal models and case reports, facilitating kidney stone passage and reducing calcium oxalate crystal deposition. While these findings are positive, large-scale human RCTs are needed to confirm efficacy. Preclinical in vitro studies have also shown strong antiviral activity, particularly against rotavirus, with high selectivity and potency. Secondary benefits include bronchodilation and vasodilation due to its calcium channel blocking properties, which could be beneficial for respiratory and cardiovascular health. Preliminary reports also suggest potential improvements in lipid profiles, such as an increase in HDL cholesterol. The time course for benefits varies; vitiligo treatment typically requires months, while kidney stone passage may occur within days to weeks.

How it works

The primary mechanism of action for Khella extract involves calcium channel blockade, mainly attributed to its active compounds, visnadin, visnagin, and khellin. These compounds interact with L-type calcium channels found in vascular and bronchial smooth muscle, leading to their relaxation. This relaxation results in vasodilation, which reduces peripheral resistance and improves blood flow, and bronchodilation, which can alleviate respiratory symptoms. In the urinary system, its diuretic effect aids in the passage of kidney stones. For dermatological applications, particularly in vitiligo and psoriasis, Khella exhibits a photosensitizing action similar to psoralens, enhancing the effectiveness of phototherapy by making skin cells more responsive to UV light. While specific pharmacokinetic data are limited, oral administration of standardized extracts has shown efficacy in both clinical and animal studies.

Side effects

Khella extract is generally well tolerated in clinical studies, with both topical and oral uses reported without serious adverse effects. The most common side effects, occurring in over 5% of users, include mild gastrointestinal discomfort and photosensitivity reactions, especially when combined with UV exposure. Uncommon side effects (1-5%) may include possible allergic reactions or skin irritation, particularly with topical application. Rare side effects (less than 1%) have not been significantly reported in the available literature. Due to its calcium channel blocking properties, there is a potential for additive effects when Khella is used concurrently with other calcium channel blockers or photosensitizing agents, warranting caution. Khella is contraindicated in individuals with known hypersensitivity to the plant or its components. Caution is also advised during pregnancy and lactation due to limited safety data in these populations. Data on use in children and the elderly are limited, and medical supervision is recommended for these groups.

Dosage

The minimum effective dose for Khella extract, specifically oral khellin, has been observed at 100 mg daily when used as an adjunct therapy for psoriasis and vitiligo in clinical studies. Optimal dosage ranges typically involve extracts standardized to 12% khellin, with daily oral doses around 100 mg of khellin, or topical formulations used in conjunction with phototherapy. The maximum safe dose for Khella extract is not well established in humans, although animal studies have used higher doses without reported toxicity. For vitiligo, topical khellin is typically applied prior to UV exposure to enhance its photosensitizing effects. For kidney stones, oral dosing is usually daily for one to two weeks or longer, depending on the individual's condition. Oral standardized extracts are used for systemic effects, while topical formulations are preferred for dermatological applications. While no specific cofactors are required, phototherapy is essential for maximizing the benefits in skin conditions like vitiligo.

FAQs

Is Khella extract safe?

Generally, Khella extract is considered safe with mild side effects. However, individuals prone to photosensitivity should use it under medical supervision, especially if exposed to UV light.

How long before effects appear?

Improvements for vitiligo typically require several months of consistent use. For kidney stones, relief or stone passage may be observed within days to weeks.

Can it be used alone for vitiligo?

While some effects may occur, the best results for vitiligo are seen when Khella extract, particularly topical khellin, is combined with phototherapy, such as a 308-nm excimer lamp.

Does it interact with medications?

Yes, there's a potential for interactions with other calcium channel blockers and photosensitizing agents. Always consult a healthcare provider before combining Khella with other medications.

Is it effective for kidney stones?

Some evidence from animal studies and case reports suggests it can facilitate stone passage and reduce crystal deposition. However, large-scale human randomized controlled trials are still needed to confirm its efficacy.

Research Sources

https://pmc.ncbi.nlm.nih.gov/articles/PMC10050252/ – This source discusses the antiviral activity of Khella seed extract, specifically its strong inhibition of rotavirus replication in vitro. It highlights an EC50 of approximately 2 μg/mL and a high selectivity index, suggesting potent antiviral effects without cytotoxicity. This preclinical study indicates a promising area for future research into Khella's therapeutic potential.
https://www.drugs.com/npp/khella.html – This source provides a general overview of Khella, including its traditional uses, chemical constituents, and some research findings. It mentions its diuretic effects for kidney stones and its use in psoriasis, often citing older studies or animal models. It also touches upon the calcium channel blocking properties of its active compounds.
https://link.springer.com/article/10.1007/s13555-017-0218-x – This article describes an open-label prospective study on the use of topical khellin combined with 308-nm excimer lamp phototherapy for vitiligo. The study, involving 20 patients over one year, reported that 45% achieved excellent repigmentation. While promising, the study's limitations include a small sample size and the absence of a control group.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4660521/ – This source discusses the pharmacological properties of *Ammi visnaga*, focusing on its active compounds like khellin and visnagin. It explains their mechanism of action, particularly their calcium channel blocking effects leading to vasodilation and bronchodilation. It also touches upon its traditional uses and potential applications in various conditions.
https://d-nb.info/1153107155/34 – This source, likely a dissertation or a detailed report, provides further context on the study by Saraceno et al. (2017) regarding topical khellin and 308-nm excimer lamp for vitiligo. It reiterates the finding of good to excellent repigmentation in a significant percentage of patients, reinforcing the potential of this combination therapy despite the study's limitations.