The study, conducted by GFC Life Science Co Ltd, suggested that this plant extract could solve a long-standing hurdle for formulators, as natural enzymes tend to lose their potency when exposed to heat during manufacturing or storage.
Unlike traditional chemical exfoliants like alpha hydroxy acids (AHAs), which can cause irritation by lowering the skin’s pH, enzymatic exfoliants are typically gentler. Still, their fragile nature has limited their cosmetic use.
The team investigated the cosmetic potential of a keratin-degrading enzyme extracted from bitter melon fruit. This plant is widely used in traditional medicine across Asia and Africa, but its specific proteolytic enzymes — those capable of breaking down proteins such as keratin — have remained largely underexplored for topical skin care applications.
In the cosmetics industry, the go-to enzymatic exfoliants are often papain (from papaya) or bromelain (from pineapple). While effective, these ingredients are notoriously sensitive. They often require cold-chain logistics or specialised encapsulation to remain active in final creams or serums.
This study sought to determine if bitter melon could provide a more robust alternative for manufacturers looking for clean label and food-grade bioactive ingredients.
The researchers compared the bitter melon enzyme against proteases from papaya and date palm.
While papain exhibited maximal activity at 37°C, it rapidly lost its function at temperatures above 50°C. In contrast, the bitter melon enzyme retained over 80% of its activity even after being held at 70°C for five days. Short-term tests suggested that heat may actually activate the enzyme rather than destroy it.
“This unique property was consistent with previous findings on aspartic proteases isolated from bitter melon, which also demonstrated increased activity upon heating,” the researchers noted.
This means the ingredient can withstand the heat of the emulsification process without losing the “peeling” efficacy.
Precision exfoliation and pH versatility
The study identified the extract as an aspartic protease. This classification is significant, as it explains the ingredient’s robustness across a wide pH range.
While many enzymes only function in a very narrow window, the bitter melon enzyme maintained over 75% of its peak activity between pH 5.0 and 9.0.
This flexibility is a major advantage for formulators. Whether in an acidic foaming cleanser or a neutral leave-on overnight mask, the enzyme will remain stable. Importantly, an ingredient that does not require an entire formulation to be built around its specific survival needs is highly valuable.
To understand how the enzyme works on the skin, the team focused on its keratinolytic activity.
The stratum corneum is made of keratin-rich cells. When the natural renewal process slows down due to age or stress, these cells build up, causing a dull, rough complexion. The bitter melon enzyme specifically targets and degrades this insoluble keratin, resulting in a smoother surface without the burning sensation often associated with chemical peels.
Proving clinical benefits for skin health
Beyond laboratory observations, the researchers conducted a four-week clinical trial involving 11 adult volunteers aged 49 to 55. The participants applied a 0.5% bitter melon enzyme solution to their faces twice daily after cleansing.
The results showed a coordinated improvement in the skin’s physical condition. The desquamation index, which measures the amount of scaly dead skin on the surface, dropped by 49.88% over a four-week period. This was a significant reduction that translated to a visible increase in skin clarity.
Furthermore, skin surface smoothness improved by 26.04%. Unlike many exfoliants that leave the skin feeling dry or tight after removing surface cells, the bitter melon enzyme in fact boosted hydration levels. Stratum corneum hydration increased by nearly 17%, while water content in the deeper layers rose by almost 20%.
“The present in-use clinical study provides human evidence that a plant-derived keratinase can simultaneously improve desquamation, skin texture, and hydration without irritation,” the researchers stated.
Crucially, none of the participants reported any adverse reactions or signs of redness throughout the study, confirming the formulation’s safety profile for sensitive skin types.
Anti-ageing potential
The study also explored the enzyme’s bioactivity beyond simple exfoliation. In-vitro tests on RAW 264.7 macrophage cells showed that the extract inhibited nitric oxide production, indicating significant anti-inflammatory properties.
This suggested that while the enzyme could exfoliate, it also worked to soothe the skin — a rare combination in the peeling category.
Furthermore, the enzyme showed a clear dose-dependent ability to inhibit elastase. Because elastase is the enzyme responsible for breaking down elastin, this suggested the bitter melon extract could pull double duty as a preventative anti-ageing active. At an 8% concentration, the extract achieved over 50% inhibition of elastase activity.
A future for enzymatic skin care
The researchers noted that this naturally sourced keratinase addressed the key limitations associated with conventional plant-derived cosmetic enzymes.
By overcoming the thermal and formulation stability constraints that have long held back natural proteases, bitter melon could open the door for a new generation of high-stability, high-efficacy natural cosmetics.
Despite the relatively limited sample size, this pilot study showed “coordinated multi-dimensional improvement” in the skin parameters that marked a promising step forward for the cosmetics industry.
Source: Cosmetics
“A Thermostable Aspartic Protease from Bitter Melon (Momordica charantia) as a Novel Cosmetic Enzyme for Skin Exfoliation and Hydration: Enzymatic Stability and Pilot In-Use Skin Benefits”
https://doi.org/10.3390/cosmetics12060281
Authors: Park Somi, et al
