Nigella seeds show promise for acne

An extract of Nigella seeds within a topical gel formulation has shown promise as a potential treatment for acne vulgaris in a study conducted in Sri Lanka,¹ where Nigella seeds are used in traditional medicines for treating acne.

The researchers say their study, published in Scientific World Journal, opens “the possibility of developing commercial products” using the seeds for the management of acne vulgaris while at the same time “rationalizing” its use as a remedy for acne in traditional medicine.

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The active ingredients of commercial medicines are often derived from natural ingredients, such as plants and spices, that have a long track record of use in traditional medicine. The seeds of the spice Nigella sativa L (black cumin) have been used for centuries in several cultures for the treatment of a variety of dermatological disorders, including burns, wounds and skin inflammatory conditions such as acne vulgaris.² In Sri Lanka, the seeds are found in several topical traditional medicine formulations used to treat acne vulgaris, eruptions of the skin and related skin diseases.³

While there are many anecdotal reports of the effectiveness of Nigella seeds, there has been limited scientific investigation to confirm these effects. Researchers in Sri Lanka therefore developed topical cosmeceutical formulation incorporating N. sativa and evaluated the antibacterial activity of those formulations against acne-causing bacteria.
Dried N. sativa seeds were soaked in ethyl acetate for 24 hours in a shaker and the solvents evaporated using a rotary evaporator to create an extract which was used to prepare three topical gel formulations of different strengths, based on the strengths used in traditional medicines.

The gel incorporated cetyl alcohol, an emollient, and moisturizer to reduce the inherent irritating property in N. sativa, as well as fuller’s earth for the absorption of excess sebum present in the facial skin. Phenoxyethanol was included as the preservative along with EDTA to stabilize the formulation from rancidity and consequently to enhance the aesthetic appeal of the product as well as the water washability of the gel. Rosewater was used as the vehicle as “it is assumed that rosewater could assist in maintaining the pH while reducing erythema, dermatitis and eczema, owing to its anti-inflammatory potency,” the researchers note. The pH value of the formulations was 5–6, and the optimal pH of the skin is 5.5.

Acne vulgaris is triggered by the activity of bacterial species such as Cutibacterium acnes (formerly Propionibacterium acnes), Staphylococcus aureus and Staphylococcus epidermidis, and growing antibiotic resistance amongst these microorganisms to antibiotics has prompted efforts to look for new treatment approaches.

To determine their antibacterial activity, the three gel formulations of (5%, 10% and 15% N. sativa extract) were dissolved in methanol and placed in wells on agar plates inoculated with S. aureus and C. acnes. A synthetic commercial antiacne gel, along with the gel base and methanol, acted as  controls (positive and negative respectively). The commercial antiacne gel contained sulfur, isopropyl methylphenol, stearyl glycyrrhetinate, vitamin E and vitamin B6 as active ingredients.

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The 5%, 10% and 15% N. sativa gels produced circles of inhibition against S. aureus, 8.0 ± 0.0mm,  9.3 ± 0.5mm and  10.6 ± 0.5mm respectively, while commercial gel produced a circle of inhibition of 8.3 ± 1.5mm. Against C. acnes the N. sativa gels’ circles of inhibition were 8.0 ± 0.0mm, 8.0 ± 0.0mm and 9.0 ± 0.0 with increasing strength, and commercial gel’s circle was 10.5 ± 0.7mm. In both cases, the gel base and methanol produced no circles of inhibition.

The gel formulations demonstrated good stability at 30 days and the antimicrobial activity against S. aureus was retained with the three formulations producing zones of inhibition of 10.5 ± 0.7, 11.5 ± 0.7, and 12.0 ± 0.0mm in diameter according to increasing strength. The formulations were also well tolerated, only 7 of 10 participants (14%) developed some signs of hypersensitivity after the application of the herbal gel formulation.

The minimum inhibitory concentration (MIC) values against S. aureus were 250, 62.5, and 62.5μg/mL for the 5, 10 and 15% N. sativa gel strengths respectively. The MIC value of the synthetic commercial antiacne gel was 125 μg/mL, indicating the 10 and 15% gels had a more potent antibacterial activity compared with the synthetic product. The major limitation of the study was the lack of MIC values of the gel formulations for C. acnes due to their limited laboratory facilities, the researchers say.

“The present study provides new insight into the possible antiacne effect of topical gel formulations incorporated with the extracts of N. sativa,” says lead researcher Mayuri Napagoda of the Department of Biochemistry, Faculty of Medicine, University of Ruhuna, Galle, Sri Lanka.

“Further investigations are warranted with a larger number of healthy human volunteers to determine any adverse effects that could be associated with the application of these formulations on human skin and thereby to determine the suitability to develop as commercial products.”

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References:

1. Nawarathne NW, Wijesekera K, Wijayaratne WMDGB, Napagoda M. Development of Novel Topical Cosmeceutical Formulations from L. with Antimicrobial Activity against Acne-Causing Microorganisms. ScientificWorldJournal. 2019;2019:5985207.

2. Eid AM, Elmarzugi NA, Abu ayyash LM, Sawafta MN, Daana HI. A Review on the Cosmeceutical and External Applications of. J Trop Med. 2017;2017:7092514.

3. Jayaweera DMA.  Medicinal Plants (Indigenous and Exotic) Used in Ceylon, Vol. 4, National Science Council, Colombo, Sri Lanka, 1982.