# Natural Photosensitizers in Clinical Trials
## 6 Conclusions  
The selection of an appropriate photosensitizer is one of the most important steps in photodynamic therapy and is crucial to the efficacy of PDT. The ideal photosensitizer must meet a number of criteria, including lack of toxicity in the dark, solubility in suitable solvents, high absorption coefficient in the wavelength range for tissue penetration, and selective binding to the target tissue. Findings to date indicate that naturally occurring compounds can act as photosensizers. Some of them have already been tested in clinical trials. The clinical work conducted so far has confirmed the overall safety of natural PSs. No serious, dangerous side effects have been observed in any of them. In some indications, natural PSs have proven more effective than synthetic ones. These are valuable papers providing information on the first effective therapeutic regimens for photodynamic therapy using PSs of natural origin. At the same time, these are only initial observations, in which a small number of indications have been tested and few therapeutic regimens have been tested. As presented in our work, natural PSs have been the most clinically tested in dental treatment. In dentistry, bacterial infections that lead to caries, gingivitis, or periodontal disease are a common problem. Photodynamic antibacterial therapy is effective and minimally invasive, making it particularly attractive for treating and preventing oral infections. Compounds of natural origin are often more readily available and less expensive to produce, allowing them to be more widely studied and facilitating potential large-scale introduction into the clinical setting, so the work described above provides an attractive basis for further research. As demonstrated in this review, the number of natural photosensitizers untested clinically is impressive, which creates the potential for extensive testing in various clinical indications. The production of natural photosensizers presents many challenges. They often have a complex chemical structure, making them difficult to isolate on an industrial scale. It is also critical to obtain a high-purity product that retains the correct biological activity. An additional challenge, especially for natural compounds, is the chemical and biological stabilities of photosensizers, which can degrade when exposed to light, oxygen, or temperature. For some natural PSs, appropriate pharmaceutical formulations may need to be developed to ensure effective delivery of the photosensitizer to its target site in the body. All of these challenges come at a potential cost for the widespread implementation of natural photosensitizers in the future. Moreover, photosensitizers of natural origin with optimal properties also provide an attractive basis for the synthesis of artificial compounds, which could also contribute to increasing the number of photosensitizers used in the clinical setting. However, further work is needed. These should be based on standardizing the extraction and production of natural photosensitizers to ensure consistency and reproducibility of established therapeutic properties. Further research is needed on efficacy, safety, and determination of the optimal therapeutic regimen for specific indications. Choosing the right photosensitizer is the basis of PDT's effectiveness, so the discovery of compounds with ideal properties is the cornerstone of this therapy's development.