*Article* **Structural Requirements for Antimicrobial Activity of Phenolic Nor-Triterpenes from Celastraceae Species**

**Laila Moujir 1, Manuel R. <sup>L</sup>ópez 1, Carolina P. Reyes 2, Ignacio A. Jiménez 2 and Isabel L. Bazzocchi 2,\***


Received: 27 June 2019; Accepted: 19 July 2019; Published: 24 July 2019

#### **Featured Application:Identifying the structural requirements of phenolic nor-triterpene framework as potential antimicrobial agents.**

**Abstract:** The emergence of pathogenic bacteria-resistant strains is a major public health issue. In this regard, natural product scaffolds offer a promising source of new antimicrobial drugs. In the present study, we report the antimicrobial activity against Gram-positive and Gram-negative bacteria and the yeas<sup>t</sup> *Candida albicans* of five phenolic nor-triterpenes (**1**–**5**) isolated from *Maytenus blepharodes* and *Maytenus canariensis* in addition to four derivatives (**6**–**9**), three of them reported for the first time. Their stereostructures have been elucidated on the basis of spectroscopic analysis, including one-dimensional (1D) and two-dimensional (2D) NMR techniques, spectrometric methods, and comparison with data reported in the literature. To understand the structural basis for the antimicrobial activity of this type of compounds, we have performed an in-depth study of the structure–activity relationship (SAR) of a series of previously reported phenolic nor-triterpenes. The SAR analysis was based on the skeleton framework, oxidation degree, functional groups, and regiosubstitution patterns, revealing that these aspects modulate the antimicrobial activity.

**Keywords:** *Maytenus*; celastroloids; semisynthesis; antibacterial activity; structure–activity relationship
