Sophie Power – Life Science, Year 2
Introduction
The growing environmental impact of chemical sunscreens, coupled with increasing concerns about their effects on human health, has intensified the search for natural ultraviolet (UV) protection alternatives (Ruszkiewicz et al., 2017). Current sunscreen solutions fall into two categories: physical and chemical compounds. Physical sunscreens, also known as mineral sunscreens, traditionally use photoprotective products like zinc oxide (ZnO), talc, iron oxide (Fe2O3), titanium dioxide (TiO2), calamine, ichthammol, and magnesium oxide (MgO) (Ajoa et al., 2024). These compounds create white casts—a protective film layer on the skin. Yet, Ajoa et al. (2024) point out that mineral sunscreens with white casts are becoming less popular, particularly among people with darker complexions, as they can create an unnatural, washed-out appearance.
This shift in consumer preference has led to increased adoption of chemical sunscreens. Unlike their mineral counterparts, chemical variants do not produce white casts because they are primarily absorbed into the epidermis (Sander et al., 2020). Once absorbed, these compounds capture UV radiation and transform it, releasing it as heat (Sander et al., 2020). Typical chemical sunscreens contain compounds such as bemotrizinol, avobenzone, bisoctrizole, benzophenone-3 (BZ-3, oxybenzone), and octocrylene (Latha et al., 2013). These serve as highly effective UVA and UVB filters. Additionally, Latha et al. (2013) note that many chemical sunscreens include insect repellent compounds to prevent insect-borne infections and irritations.
However, chemical sunscreens present significant health and environmental concerns. Since these products are absorbed by the epidermis, their compounds enter the bloodstream. Ruszkiewicz et al. (2017) identify several neurotoxins commonly present in mainstream sunscreens, including octyl methoxycinnamate, benzophenone-3 and -4, 4-methylbenzylidene camphor, 3-benzylidene camphor, and octocrylene. These compounds have been linked to DNA, protein, and lipid damage. Chemical sunscreens also introduce non-water-soluble compounds to corals and are directly connected to bleaching and reduced green algae production by disrupting critical ecological cycles in marine environments (Danovaro et al., 2008). Natural UV filters, particularly those found in plants with aromatic ring compounds, have emerged as promising candidates for more natural sun protection (Li et al., 2023) and fall under the physical sunscreen category. In the same research by Li et al. (2023), they demonstrated the potential of plant-based alternatives, with certain species like common blackberry (Rubus allegheniensis), showing sun protection index (SPI) levels ranging from 37 to 54 in the sun protector factor range (SPF), where standard sunscreens fall under the range of 6-50. These findings suggest that the evolved UV resistance of plants could offer effective protection while minimizing environmental impact. Furthermore, water-soluble natural compounds like ethylhexyl pelargonate show promise in reducing white cast issues while maintaining protective properties (Del Olmo et al., 2022).
Although research has explored plant-based UV protection globally, there remains a significant gap in understanding the photoprotective properties of native plants in British Columbia, Canada. This region’s diverse ecosystems and unique flora may house untapped potential for effective, sustainable UV filters. While it may not be realistic for every region to rely solely on local plants for sunscreen production, identifying promising compounds in BC’s native species could contribute valuable alternatives to the broader market. If an effective and eco-friendly photoprotective compound were found, it could be developed for wider use and even manufactured or exported, benefiting both local biodiversity conservation and global sun protection efforts. Additionally, this research supports the integration of Indigenous plant knowledge into mainstream STEM applications, emphasizing the importance of regional studies in the global search for natural solutions.
This study investigates four native British Columbia plant species: Oregon Grape (Mahonia aquifolium), Pacific Dogwood (Cornus nuttallii), Western Sword Fern (Polystichum munitum) and Redwood Sorrel (Oxalis oregana) (Figure 1). Previous research has identified promising photoprotective compounds in some of these species. Pacific Dogwood contains multiple protective substances, including ursolic acid, gallic acid, and various vitamins (Deng et al., 2024), while Oregon Grape features several flavonoids known for their skin health benefits and excellent epidermal absorption (Higbee et al., 2023). Notably, Western Sword Fern and Redwood Sorrel remain largely unstudied for their photoprotective properties, presenting an opportunity for novel discoveries in natural UV protection. These species were also selected due to their abundance and availability throughout the province as well as their uses in Indigenous communities.
Figure 1: Native British Columbia plant species. A: Pacific Dogwood (Cornus nuttallii). Source: Picture This. B: Redwood Sorrel (Oxalis oregana). Source: Fine Gardening C: Oregon Grape (Mahonia aquifolium). Source: Wikipedia. D: Western Sword Fern (Polystichum munitum) Source: Grow Happier Plants.
Pacific Dogwood, Western Sword Fern, and Redwood Sorrel have the most notable Indigenous uses. Pacific Dogwood, when used medicinally, is said to help with treating skin infections, fevers, and digestive issues, and is used as an antiseptic (Camosun College, 2025). These traits could prove desirable in a sunscreen-related product. Western Sword Fern’s main utilization is for treating skin boils and sores (Lake Wilderness Aboratorium, 2016), which can provide additional comfort and soothing properties when incorporated into sunscreen products. Regarding Redwood Sorrel, most of its uses are nutritional, but it has also been used as treatments for helping rheumatism and eye sores (Gifford, 1967).
The implications of this research extend beyond the immediate goal of locating natural sunscreen candidates. Understanding the UV resistance mechanisms of these native plants could inform broader areas of ecological research and conservation efforts. Additionally, this study contributes to the growing body of knowledge about sustainable solutions for human health protection while preserving marine ecosystems. As climate change intensifies UV exposure concerns and environmental preservation becomes increasingly critical, identifying effective, environmentally compatible UV protection methods takes on greater urgency.
This investigation represents the first comprehensive study of these specific British Columbia native plants for UV protection properties. By examining local species that have evolved under regional UV exposure conditions, this research may uncover novel photoprotective compounds that could revolutionize sustainable sunscreen development while supporting local biodiversity conservation efforts.
Methods and Materials
This study used a microscope and essential materials for the preparation of slide samples, including glass slides, slide covers, and a scalpel, which were used to extract sample specimens from plant clippings.
Plant clippings were sourced from four distinct species: Oregon Grape, Pacific Dogwood, Western Sword Fern, and Redwood Sorrel. The clippings themselves were obtained from Science World, BC, Canada, and Jericho Beach, BC, Canada. For each species two clippings were obtained—one designated for the control group and the other for the treatment group.
The treatment group was placed in an opaque box where they were exposed to UVA radiation. The control group was placed in an opaque box as well, but no additional variables were added so general decay could be monitored. The procede began with the two clippings from each of the species being placed into the opaque boxes, after which the UVA lamp was installed into the treatment group’s box. The clippings were then left for two weeks, during which time they were monitored every other day.
For microscopic observation, a portion was excised from each clipping — both from the control and experimental groups — using a scalpel and then positioned onto a glass slide. Systematic observations were conducted, and data was collected every two days at 40x magnification to assess the prevalence of cells exhibiting signs of cancer, decay, or distortion. One such sign of decay were crown galls. Crown galls are areas of a plant’s leaves, roots, or stems that have a deformed cells and cell wall. It is a symptom of decay in plants as are caused by carcinogens or disease. It is frequently compared to cancer in animals but does not spread the same way due to the cell wall’s presence in plant cells (Kado, 2014). The abundance of cells showing abnormalities was measured in percentage relative to the field of view (FOV) of the microscope.
To enhance the reliability of the findings, observations were repeated within the same session to identify potential outliers, refining the accuracy of the calculated averages. After a two-week observation period, the protocol was repeated using fresh clippings from the same sample sites, and this cycle continued for several weeks. Each observation session was logged to ensure comprehensive documentation of all findings, with three rounds of observations completed.
Results
From the experimental process where Oregon Grape, Pacific Dogwood, Western Sword Fern, and Redwood Sorrel were observed for the amount of decay they experienced under constant UV exposure and without. The treatment group showed more traits of decay in comparison to the control group (Figure 2). The UV treatment group showed decay traits 31 times, whereas the control group showed them 27 times (Appendix A). Species that showed the least amount of crown gall related decay were the Redwood Sorrel and Pacific Dogwood, where they showed a decay increase of 1.0% and 4.9% (Table 1). For example, Pacific Dogwood’s decay rate peaked at ~8.5% in treatment versus ~3.5% in control, where the Redwood Sorrel showed no decay in the control and only ~1% when in the treatment group (Table 1).
Figure 2: Average Maximum Crown Gall related Decay per Species (Error bars are used as measurements could have been impacted by human error when measuring the amount of crown gall related decay is present.) (Bar not present for the control of Redwood Sorrel as no crown gall related decay was present in observations.)
Table 1: Average Crown Gall Presence per Species (Redwood Sorrel has 0% in the control group due to no decay being present during observations.)
Additional observations and trends noted include how the Oregon Grape treatment group showed crown galls and discoloration in all samples, with no additional traits noted. In the control group, crown galls appeared in half of the Oregon Grape samples, discoloration in two-thirds, and vein decay in one-third (Table 2). In the treatment group for Pacific Dogwood, crown galls were seen in 75% of samples, discoloration in all, and vein decay in one. In the control group, crown galls also appeared in 75% of samples, discoloration in two, and vein decay in two (Table 2). For the Western Sword Fern, the treatment group showed crown galls in 75% of samples, discoloration in two, and vein decay in one. In the control group, dehydration was observed in 75% of samples, discoloration in two, and both crown galls and vein decay in one (Table 2).
Table 2: Present Traits of Decay and Presence in of According Samples
In Redwood Sorrel’s treatment group, cell distortion was present in all samples, discoloration in 66%, and cell wall oxidation and dehydration each once. In the control group, the same cell distortion and discoloration were observed, along with one instance of dehydration and cell wall oxidation (Table 2).
Discussion
Redwood Sorrel showed the most promising photoprotective results among all tested species. In the control group, it exhibited no crown galls and only minimal signs of decay such as mild discoloration and cell wall oxidation. In the UVA-treated group, the decay traits remained low, with crown gall-related decay averaging just 1.0%. This was the lowest increase in decay among all species, indicating potential UV resistance. The presence of oxalic acid, a compound known for various biochemical activities (Tuazon-Nartea et al., 2013), may contribute to these protective properties. While there is little existing research on Redwood Sorrel’s UV resilience, its stable performance under UV stress highlights it as a highly viable candidate for natural sunscreen development. This species warrants further investigation into its chemical profile to isolate any UV-absorbing compounds that could be used in eco-friendly sun protection formulations.
Western Sword Fern demonstrated moderate photoprotective potential. Although the species showed more decay in the treatment group than in the control, the relative decay remained relatively low. The crown gall-related decay increased from 1.8% in the control group to 6.9% in the treatment group—a 5.1% difference, the largest change among all species. This suggests that while it may not have strong inherent photoprotective properties, its baseline resistance to decay is somewhat consistent. There is currently little to no formal research into Western Sword Fern’s UV protection capabilities. However, its traditional Indigenous use in treating skin sores and boils (Lake Wilderness Arboretum, 2016) might hint at some protective or healing chemical components that could be of interest in future photoprotection studies.
Pacific Dogwood yielded mixed results. It showed a 4.9% increase in crown gall-related decay when exposed to UV radiation (from 3.8% to 8.6%). Despite this increase, the species consistently exhibited high relative levels of decay in both the treatment and control groups, which may suggest a general susceptibility to tissue degradation. However, the smaller percentage difference between the control and treatment groups implies some level of inherent UV protection. Previous studies (Deng et al., 2024) have identified photoprotective compounds such as ursolic acid, gallic acid, and various vitamins in Pacific Dogwood, which might explain its relative resistance to additional UV-induced damage. Its traditional medicinal uses — especially in treating skin conditions (Camosun College, 2025) — support the idea that it could still offer valuable compounds for photoprotection, though perhaps in combination with other, more UV-resistant species.
Oregon Grape was the least successful candidate in this study. It showed high relative levels of decay in both control and UV-exposed groups, with the crown gall-related decay increasing from 3.5% to 8.5% (a 5.0% difference). Additionally, all UV-exposed samples showed crown galls and discoloration, indicating high sensitivity to UV radiation. Despite previous research highlighting the skin-benefiting properties of Oregon Grape’s flavonoids and good epidermal absorption (Higbee et al., 2023), the observed results suggest a lack of effective UV resistance. The severity and frequency of decay traits in both groups raise doubts about its usefulness as a standalone photoprotective agent. While it may have other therapeutic or cosmetic applications, Oregon Grape does not appear to provide significant UV shielding in this context.
Potential sources of error in this experiment include the moisture levels, temperature, darkness, and intensity of the UV lamp were not constantly monitored, and changes in these factors could have affected the decaying process of the clippings. Specifically, the UV lamp may have lost intensity over time due to bulb degradation. Additionally, there may have been periods when the lamp was not fully centered on the clippings in the UV group, altering the amount of radiation received.
All plant samples were collected from outdoor areas, so the temperature and weather at the time of collection — and in the weeks prior — may have influenced the overall health and integrity of the plants. Furthermore, not all species’ clippings were taken from the same individual plant, except for the Redwood Sorrel, due to not having consistent access to the same plant. This introduces natural variation in sample health.
Future experiments could explore the chemical profiles of Western Sword Fern and Redwood Sorrel to identify compounds that might contribute to UV resistance. Further research could also test additional native BC plant species for UV resilience, as well as investigate the effects of varying UV strengths and wavelengths on plant decay patterns. Research into why certain species experienced certain types of decay more than others could be an insightful look into the chemical makeups of different species of plants and how it influences its decay
Conclusion
The purpose of this investigation was to gather insight on the photoprotective properties of different native British Columbian plant species. Resulting data showed that Redwood Sorrel showed the least decay in the amount of traits present and in severity of them as well. This could indicate that it is a more operable candidate to be incorporated into sunscreens. Pacific Dogwood and Western Sword Fern showed possible candidacy, but not as highly as Redwood Sorrel. Because of this, we recommend further research into the properties of Redwood Sorrel including development and testing extracts from the species in sunscreens to assess viability of commercial sunscreen applications.
References
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Appendix A
Table 1A: Decay Traits Present in Samples (Yes, No, Not Available)
Appendix B
Figure B1: Average Percentage of Crown Galls Present in Treatment (%) (Error bars are used as measurements could have been impacted by human error when measuring the amount of crown gall related decay is present.) (No bars for Redwood Sorrel showed for Week 1 day 1- Week 2, day 2, due to no crown gall related decay being present.)
Figure B2: Average Percentage of Crown Galls Present in Control (%) (Error bars are used as measurements could have been impacted by human error when measuring the amount of crown gall related decay is present.) (Redwood Sorrel not shown as no decay regarding crown galls was noted in the control group for this species.)