Ten novel 1,3,4-oxadiazole analogs (A-J) were prepared and tested in terms of their antibacterial and antioxidant properties. The obtained compounds were identified by the determination of melting points, thin-layer chromatography, and the confirmation of molecular formulas, whereas the identification of representative compounds proceeded by adding the UV- Visible spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (¹H- and ¹C-NMR) methods. The spectral analyses proved the successful construction of the oxadiazole nucleus and the existence of the typical functional groups. The synthesized derivatives were evaluated with respect to the Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) and Gram-positive bacterium (Staphylococcus aureus and Micrococcus luteus) regarding their antibacterial activity based on the agar diffusion test with 100 µg/mL, 500 µg/mL, and 1000 µg/mL concentrations of the derivatives. In a concentration-dependent fashion, several compounds showed a significant level of antibacterial activity. Out of them, methyl-substituted (B) and chloro-substituted (D) counterparts exhibited similar inhibition zones as the standard drug ciprofloxacin. The DPPH free radical scavenging assay was used to determine the antioxidant activity. These findings revealed moderate-strong antioxidant potential of most compounds, with some halogenated derivatives having lower IC50 values compared to ascorbic acid. Possible structure-activity relationship analysis showed that electron-withdrawing and electron-donating substituents have a significant impact on biological activity. All in all, the results demonstrate substituted 1,3,4-oxadiazole derivatives as promising candidates in the further development as antimicrobial and antioxidant agents.

Quantification of active components in dermatological formulations, especially, Hydroquinone, Tretinoin and Salicylic Acid is also an important element of pharmaceutical quality control. These two ingredients are usually used together to treat skin diseases including hyperpigmentation, acne, and psoriasis because of the complementary properties. This review will examine the current developments in the Reverse Phase High-Performance Liquid Chromatography (RP-HPLC) methods of simultaneous analysis of the three actives. The main aspects to be focused on are column choice, mobile phase optimization, wavelengths of detection and outcomes of method validation. The development of Ultra High-Performance Liquid Chromatography (UHPLC) which has been observed has greatly accelerated speed and sensitivity of analysis through the use of smaller particle sizes and faster run time and the development of advanced detectors like Photodiode Array (PDA) detectors has also enhanced the ability to detect several compounds simultaneously. Moreover, there is a move in trends towards green chromatography and automation which is making the methods of analysis increasingly sustainable and efficient. However, issues like complexity of matrices, co-elution and degradation of actives are present and thus there is still need to develop more on stability-indicating techniques and measuring all the three actives simultaneously in one technique. This review highlights the importance of these innovations towards enhancing the effectiveness, safety, and regulatory conformance of dermatological procedures.