Pomegranate
Chase Kempinski, PhD (chase@tritera.co)
Author’s note: my objective in writing these posts is to keep with our theme of skincare but also to highlight interesting facts about every plant species that we discuss. I wish to keep the writing somewhat more colloquial than would be expected if this were a traditional scientific journal article or technical writing. I find the world of plants astounding, from their incredible arrays of anatomies (some of which have persisted millennia) to their specialized cellular biochemistries, and one topic which I am particularly fascinated by, the suite of small molecules which they produce. These are the specific compounds which us humans have found so helpful over the years. Prime examples are morphine (helpful but infamous painkiller), paclitaxel (commercially delivered as the chemotherapeutic, Taxol), nicotine, cannabinoids, artemisinin (anti-malarial), and caffeine. There are so many more that traditional and folklore medicine have also been aware of but did not know the specific responsible molecule(s). By making tinctures, teas, or poultices from specific plant tissues, they extracted these beneficial compounds and used them in medicines or for recreation. I hope through these posts that you will consider more deeply the incredible natural chemistry that exists around you everyday.
Pomegranate arils are the delicious juice-filled coverings around the seed. They are an incredible source of antioxidants.
Biology and Chemistry of Pomegranates
When compared to other fruits, I set pomegranate apart due to its striking visual anatomy. Unlike many other fruits where the desirable portion is the soft tissue around the seed, in pomegranates, it is the fleshy seed coat that we enjoy. Specifically, it is the swollen embryonic seed coat (technically, a sarcotesta) which contains the edible portion (1). This portion of the fruit is often also referred to as an aril. An aril is a botanical term for tissue covering the seed which is derived from a portion of the plant ovule (what will develop into a new seed once fertilized) that is attached to the mother (2). Depending on the species, the aril can take on different forms where in the case of pomegranate it is a pulp-filled case around the seed. Despite this, the entire pomegranate fruit itself is considered a berry (3).
Pomegranate juice has had a wide variety of biological activities, most of which are attributed to its powerful antioxidant activity (4–6). A study in 1999 by Schubert et al. (4) showed that fermented pomegranate juice had similar antioxidant activity to the compound butylated hydroxyanisole (BHA). BHA is powerful synthetic antioxidant that is often added as a preservative to foods (although it has biological actions beyond its role as an antioxidant) (7). The compounds in Pomegranate juice which are most often attributed to this antioxidant activity are high amounts of (poly)phenolics. Plants are the main dietary source of polyphenolic antioxidants and these are generally divided into two classes: flavonoids and nonflavonoids. This division arises primarily because each is derived from a different metabolic pathway. The pulp from pomegranate arils stands out for being an incredibly rich source of nonflavonoid phenolics, specifically ellagitannins. Pomegranates also produce large amounts of an ellagitannin that was first identified in their extract, punicalagin (8). These particular polyphenolics are fairly large molecules and are not absorbed into the bloodstream directly but broken down into ellagic acid or metabolized by organisms in the microbiome of the digestive tract into urolithins (8). Being a polyphenol, ellagic acid is a powerful antioxidant, but it also evidence that it helps in preventing obesity and various metabolic diseases as well as the urolithins have been investigated for their ability to help prevent prostate cancer (9).
How does this apply to skincare?
While this establishes a lot of great reasons to eat and drink pomegranates, we have not discussed how pomegranate extract can aid in skincare. In a study using an in vitro (lab-grown) human skin model to evaluate the protective capabilities of Pomegranate juice, extract, and seed oil against UV-B radiation (10). The authors found that all three demonstrated protection against photodamage by reducing the amount of damaged DNA, damaged proteins, and having a reduction in activated signaling pathways associated with damage, photoaging, and cell proliferation. These are all markers of skin damage which can lead to premature aging, such as wrinkles, dark spots, etc. Protection against these damage markers is attributed to the strong antioxidant properties of the Pomegranate products. There several excellent reviews highlighting literature investigating the anticancer, including protection of the skin against UV damage (11–13). Overall, Pomegranate fruit products (including the oil) appear to supplement and protect the skin barrier and are an excellent demonstration of the need and power of antioxidants in protecting our skin against environmental damage.
Why Tritera is Interested
The deep chemical rationale and demonstrated capabilities are inspiring us to formulate Pomegranate oil into our Antioxidant Serum. This will offer another excellent suite of natural products to make the serum even more effective and soothing. As we continue to develop new formulations you can be assured that we will focus on using the best ingredients. This means organic, virgin Pomegranate seed oil. We will provide updates as new formulations are developed and plan to offer these in a trial program. More details on how the trial program will operate will be available later. If you are interested in the trying new products and providing feedback, please click here. Currently, we envision a small group of individuals who can purchase these new formulations at cost to provide critical feedback as we iterate towards providing the best skincare products formulated by science and backed by empirical evidence.
If you are still interested…
The species of pomegranate that is most widely cultivated is Punica granatum. It is one of only two species in the family Punicaceae. The other being P. protopunica, which is native to the Socotra Island of Yemen and known as the Socotra pomegranate, produces much smaller fruits and is not considered edible (3). The origin of the pomegranate is believed to be southwest Asia, and initially domesticated across the Middle East. There is evidence of pomegranate use dating to over 5,000 years ago. Pomegranates prefer to grow in areas with high sunlight, mild winters, and hot dry summers which allows the fruit to develop optimally. Too much rain during summer can cause the fruits to swell and split (3). Despite there being only one species, there are several varieties and growing conditions can cause these to exhibit different growing patterns. While most grow as trees, sometimes they can appear as shrubs or creeping bushes (3).
The nonflavonoid, ellagic acid, which is a powerful antioxidant present in Pomegranates. This antioxidant activity is due to the hydroxyl groups and aromatic rings.
An evaluation of 29 different varieties showed that the high antioxidant activity in the aril juice could be attributed to the polyphenol and anthocyanin contents. Interestingly, this same study homogenized the entire pomegranate and saw antioxidant levels about 20-fold higher than in the aril juice alone (14). Chemically, phenolics are compounds which have at least one aromatic ring with one or more hydroxyl groups attached (see figure of ellagic acid). It is the aromatic ring which gives phenolics their antioxidant activity, as it allows them to stabilize the lone electron that arises after hydrogen or electron donation to quench a free radical (instead of propagating the free radical cascade by passing it off to another molecule, this chain reaction that can be caused by free radicals is what makes them so destructive) (15). Flavonoids include molecules (the anthocyanins) which can give plants rich colors, imparting the deep reds, blues, and purples seen in fruits like berries, grapes, and pomegranates. The nonflavonoids include tannins and stilbenes, the main dietary stilbene being resveratrol (for an in-depth review, see 10). The pulp from pomegranate arils stands out for being an incredibly rich source of nonflavonoid phenolics, specifically ellagitannins. These ellagitannins are fairly large molecules and are not absorbed into the bloodstream directly but hydrolyzed to ellagic acid or metabolized by organisms in the microbiome of the digestive tract into urolithins (8).
References
1. R. Dahlgren, R. F. Thorne, The Order Myrtales: Circumscription, Variation, and Relationships. Ann. Missouri Bot. Gard. 71, 633 (1984).
2. S. R. Silveira, M. C. Dornelas, A. P. Martinelli, Perspectives for a framework to understand aril initiation and development. Front. Plant Sci. 7, 1–7 (2016).
3. D. Holland, K. Hatib, I. Bar-Ya’akov, “Pomegranate: Botany, Horticulture, Breeding” in Horticulture Reviews, Volume 35, J. Janick, Ed. (John Wiley & Sons, Inc., 2009), pp. 127–192.
4. S. Y. Schubert, E. P. Lansky, I. Neeman, Antioxidant and eicosanoid enzyme inhibition properties of pomegranate seed oil and fermented juice flavonoids. J. Ethnopharmacol. 66, 11–17 (1999).
5. E. Shwartz, et al., Changes in chemical constituents during the maturation and ripening of two commercially important pomegranate accessions. Food Chem. 115, 965–973 (2009).
6. M. I. Gil, F. A. Tomas-Barberan, B. Hess-Pierce, D. M. Holcroft, A. A. Kader, Antioxidant activity of pomegranate juice and its relationship with phenolic composition and processing. J. Agric. Food Chem. 48, 4581–4589 (2000).
7. N. Festjens, et al., Butylated hydroxyanisole is more than a reactive oxygen species scavenger. Cell Death Differ. 13, 166–169 (2006).
8. D. Heber, “Pomegranate Ellagitannins” in Herbal Medicine: Biomolecular and Clinical Aspects, 2nd Ed., I. F. F. Benzi, S. Wachtel-Galor, Eds. (CRC Press/Taylor & Francis, 2011), pp. 1–10.
9. I. Kang, T. Buckner, N. F. Shay, L. Gu, S. Chung, Improvements in metabolic health with consumption of ellagic acid and subsequent conversion into urolithins: Evidence and mechanisms. Adv. Nutr. 7, 961–972 (2016).
10. F. Afaq, M. A. Zaid, N. Khan, M. Dreher, H. Mukhtar, Protective effect of pomegranate-derived products on UVB-mediated damage in human reconstituted skin. Exp. Dermatol. 18, 553–561 (2009).
11. E. P. Lansky, R. A. Newman, Punica granatum (pomegranate) and its potential for prevention and treatment of inflammation and cancer. J. Ethnopharmacol. 109, 177–206 (2007).
12. V. M. Adhami, N. Khan, H. Mukhtar, Cancer Chemoprevention by Pomegranate: Laboratory and Clinical Evidence. Nutr. Cancer 61, 811–815 (2009).
13. P. Sharma, S. F. McClees, F. Afaq, Pomegranate for prevention and treatment of cancer: An update. Molecules 22, 1–18 (2017).
14. R. Tzulker, et al., Antioxidant activity, polyphenol content, and related compounds in different fruit juices and homogenates prepared from 29 different pomegranate accessions. J. Agric. Food Chem. 55, 9559–9570 (2007).
15. C. Rice-Evans, N. Miller, G. Paganga, Antioxidant properties of phenolic compounds. Trends Plant Sci. 2, 152–159 (1997).
16. D. Del Rio, et al., Dietary (poly)phenolics in human health: Structures, bioavailability, and evidence of protective effects against chronic diseases. Antioxidants Redox Signal. 18, 1818–1892 (2013).
