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October 31, 2012

Mongongo Oil: An Exotic Emollient for Natural Hair



Mongongo oil has been valued for centuries in Africa and is now gaining popularity in the rest of the world as we become educated about its beneficial qualities. Not only is the fruit extremely nutritious, but the oil has many useful properties as an emollient for both hair and skin. What makes mongongo different from other botanical oils and how does this affect its properties?

Origin

Mongongo oil is obtained by cold-pressing the nuts that come from the Mongongo or Manketti tree (Schinziophyton rautanenii). The Manketti tree is found from coast to coast in Southern Africa. It thrives in the seasonal dry lands where it weathers a broad range of temperatures from sub-freezing to scorching desert heat. It is found both sporadically scattered and also in large groves throughout northern Namibia, southern Angola, Zambia, Botswana, Zimbabwe, Mozambique and Malawi. The egg-shaped, reddish brown fruit is prized by both the people and the elephants indigenous to the region. The nuts are often gathered from elephant dung, a practice that is less labor intensive than harvesting the fruit and extracting the nut from the center.

Composition of Mongongo Oil

The nut is very high in fat (>57%) and contains a plethora of other valuable nutrients, such as calcium, magnesium, iron, copper, zinc and thiamine. Each seed contains approximately 560 mg of vitamin E (tocopherol). The antioxidant properties of this vitamin lend a high degree of thermal and oxidative stability to the oil, which greatly delays onset of rancidity of the oil, even in the intense South African heat. The oil has been greatly prized, not only for its nutritive benefits, but also as a skin and hair emollient and skin protectant.

The composition of the oil in mongongo fruit is fairly different from many other plant oils used as topical hair treatments or conditioning ingredients. It is comprised of between 40-50% polyunsaturated fatty acids, as compared to shea and coconut oil, which are comprised largely of saturated fatty acids and mango, olive, avocado, jojoba and almond oils, which are comprised mainly of monounsaturated oils.

Fatty Acid Content of Mongongo Oil:
  • 45-55% polyunsaturated fatty acids: linoleic acid, alpha-eleostearic acid
  • 17% saturated fatty acids: palmitic acid, stearic acid
  • 18% monounsaturated fatty acid: oleic acid
Unsaturated molecules have at least one carbon-carbon double bond in their structure. Double bonds are connected at a different angle than single ones and this produces a kink in the molecular geometry. This type of structure inhibits crystallization by impeding packing of adjacent molecules. For this reason, oils with high concentrations of polyunsaturated and monounsaturated fatty acids are typically either liquids at room temperature or melt readily upon contact with skin.
Stearic acid, a saturated hydrocarbon molecule with 18 carbons (relatively long-chain fatty acid) has a melting point of 69.6°C (157.28°F). Oleic acid is a monounsaturated hydrocarbon with a melting point of 10.5°C (50.9°F). Polyunsaturated acids, such as linoleic and linolenic, have multiple kinks in their chains and are liquid at very low temperatures (melt point = -5°C (23°F) for linoleic acid).

Properties of the different types of fatty acids

The protective outer cuticle layer of hair is not a solid surface, but is porous in order to allow transport of oils and water back and forth through the hair and into the cortex. The lipid-rich cell membrane complex layer just beneath the cuticle scales acts as a diffusion port, enabling fatty acids and moisture to travel into the interior of the hair strand.

Molecular size and shape determine the probability of a fatty acid to travel through the cuticle layer into the cortex of the hair. Saturated fatty acids such as stearic acid, lauric acid and palmitic acid diffuse easily through the pores of the cuticle layer and penetrate the cortex, where they provide flexibility and suppleness to hair strands. Spectroscopic studies demonstrate that despite their kinked structure due to the single double bond, monounsaturated fatty acids are also able to readily penetrate the interior of the hair via this route.

However, the more unwieldy structure of polyunsaturated fatty acids prohibits them from penetrating into the interior of the hair strand and they remain adsorbed onto the surface of the hair. Oils such as mongongo oil that are high in polyunsaturated fatty acids, form a protective and emollient film on the surface of the hair, where they act as a barrier preventing moisture from escaping the interior of the hair. These fatty acids can add gloss to hair and improve comb-ability by smoothing the surface of the hair. Due to the presence of the acid groups in their structure, these ingredients can also have a mild humectant effect.
The linoleic acid in mongongo oil is known for being emollient to the hair, and stearic acid, palmitic acid and oleic acid are good at penetrating to the cortex to supply elasticity and improved mechanical properties. Perhaps the most interesting properties of mongongo oil can be attributed to the presence of α-eleostearic acid, a conjugated trienoic fatty acid. This molecule has three double bonds in the middle of its structure that are conjugated, meaning they alternate (double bond-single bond-double bond-single bond…). These types of structures have unique chemical properties due to this conjugation, as they can delocalize certain of their electrons in response to various stimuli in a process known as resonance stabilization.

There are three reasons that this very specific feature of the organic structure of α-eleostearic acid is interesting to us in hair care applications. The first is that the conjugated diene structure enables this fatty acid to act as a mild sun protective agent via UV-absorption and subsequent resonance stabilization. The second reason is that the molecule is capable of undergoing a UV-initiated photopolymerization reaction, whereby the fatty acids molecules link together into a three-dimensional crosslinked network, forming a flexible film on the surface of the hair. This provides physical protection to the hair and also may impart style hold or curl retention. Thirdly, this polymerization mechanism (called curing) substantially reduces drying time for hair. Even once polymerized, the carboxylic acid groups on the molecule should be sufficient enough “hydrophilic handles” to permit removability in water, especially if conditioner and/or mild shampoo are used.
Since it is fun to experiment with our hair, it seems worthwhile to at least sample some of these new products containing this ingredient. Look for products that contain other quality ingredients and that feature mongongo oil sufficiently high up the ingredient list. Beware products that are comprised primarily of other oils and only include this as a trace ingredient as they may prove to not be a sound investment. Let us know your thoughts when you do try some of the new mongongo oil products.
References:
  1. Dyer, J.M., et al, http://naldc.nal.usda.gov/download/22993/PDF, Differential Extraction of Eleostearic Acid-Rich Lipid–Protein Complexes in Tung Seeds, JAOCS, Vol. 75, no. 11 (1998)
  2. Yang et al. BMC Plant Biology 2010, 10:250, http://www.biomedcentral.com/1471-2229/10/250

 Have you tried monongo oil? If so, was it pure, in a commercial preparation or mixed with other natural oils? How did you like it?

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