Squalene is a naturally occurring organic compound, specifically a triterpene hydrocarbon with the chemical formula C30H50. It is widely found across both the animal and plant kingdoms, playing a significant role in various biological processes. This compound holds considerable commercial value, finding applications in diverse industries such as cosmetics, pharmaceuticals, and nutraceuticals. Understanding its origins provides insight into both its biological importance and its commercial availability.
Squalene in Living Organisms
Squalene serves a fundamental biological role as a precursor molecule in the synthesis of essential compounds. In animals, including humans, it is a key intermediate in the biochemical pathways that produce cholesterol, steroid hormones, and vitamin D.
The human body naturally produces squalene, and it is a prominent component of human sebum, the oily substance secreted by the skin’s sebaceous glands. In sebum, squalene contributes to skin hydration, acting as a natural moisturizer and helping to maintain the skin’s barrier function. It also offers antioxidant protection for the skin, helping to defend against environmental stressors.
Plants also synthesize squalene, where it functions as a precursor for phytosterols, which are plant sterols analogous to cholesterol in animals. This biosynthetic pathway is essential for plant cell membrane structure and various physiological processes.
Shark Liver Oil as a Source
Historically, shark liver oil was the primary commercial source of squalene, and it was from sharks (genus Squalus) that the compound derived its name. Deep-sea sharks, such as those from the Centrophorus and Squalus genera, possess particularly high concentrations of squalene in their livers, often ranging from 40% to 80% of the total oil content. This abundance made shark liver a convenient and economically viable source for extraction in the past.
The squalene extracted from shark liver oil found various applications, including its use in cosmetics as an emollient and in some vaccine formulations as an adjuvant. However, the reliance on shark liver oil raised significant ethical and environmental concerns. The demand for squalene led to extensive fishing of deep-sea shark species, many of which are vulnerable to overfishing due to their slow reproductive rates.
Overfishing for squalene had a devastating impact on shark populations and marine ecosystems, prompting conservationists and environmental groups to advocate for more sustainable alternatives. This growing awareness and pressure from consumers and regulatory bodies, such as the European Union banning shark-derived squalene in cosmetics since 2009, spurred the search for other sources.
Plant-Based Squalene Sources
The growing concerns surrounding shark-derived squalene have led to the emergence and increasing importance of plant-based sources as sustainable and ethical alternatives. These plant-derived forms offer the same beneficial properties without contributing to the depletion of marine life.
Among the most prominent plant sources is olive oil, which is widely recognized as the richest and most common botanical source of squalene. Virgin olive oils can contain squalene concentrations ranging from 0.8 to 13 grams per kilogram, with some premium qualities reaching up to 700 mg per 100 grams. The squalene is often recovered from byproducts of olive oil production, such as the unsaponifiable fraction.
Other notable plant sources include amaranth oil, which can boast high squalene content, sometimes exceeding 5900 mg per 100 grams. Rice bran oil and wheat germ oil are also recognized for their squalene content, albeit typically in smaller amounts compared to olive or amaranth. More recently, squalene derived from sugarcane through biotechnological fermentation processes has gained traction as a highly sustainable option.
Obtaining Squalene Sustainably
The extraction of squalene from its various sources, whether historical animal-derived or modern plant-based, typically involves several chemical processes. Common techniques include solvent extraction, often using hexane, to separate the squalene from the raw material. Following extraction, purification steps such as molecular distillation are employed to achieve higher purity levels.
Saponification, which involves treating oils with an alkali to convert fatty acids into soap, can also be part of the process, allowing for the isolation of the unsaponifiable fraction where squalene resides. The modern focus is increasingly on developing and utilizing sustainable extraction and production methods, especially for plant-based squalene, to minimize environmental impact.
Emerging biotechnological approaches offer promising avenues for sustainable squalene production. Fermentation by microorganisms, particularly yeast such as Saccharomyces cerevisiae, has become a significant method. Genetic engineering techniques are being applied to enhance squalene yields in these microorganisms, making them a more efficient and environmentally friendly source.