*2.4. Aspergillus sp. Derived from Algae and Their Antimicrobial Activities*

Two C7-alkylated salicylaldehyde derivatives metabolites, namely asperglaucins A and B (**24** and **25**), were isolated from the endophytic fungus *A. chevalieri* SQ-8 (Figure 4). Asperglaucins A and B showed potent antimicrobial activities against plant pathogens *B. cereus* and *Pseudomonas syringae* pv *actinidae* (Psa), with an MIC value of 6.25 μM. Further analysis showed that asperglaucins A and B may change the external structure of *B. cereus* and Psa and cause cell membrane rupture or deformation. The results indicated that asperglaucins A and B may be potential lead compounds of pesticide fungicides [58].

**Figure 4.** Compounds of *Aspergillus* sp. derived from algae.

Two new diketopiperazines, namely versiamide A (**26**) and 3, 15-dehydroprotuboxepin K (**27**), were isolated from endophytic fungus *A. creber* EN-602 obtained from the marine red algae *Rhodomela confervoides*. Versiamide A and 3, 15-dehydroprotuboxepin K showed inhibitory activities against a variety of aquatic bacteria, with MIC values ranging from 8 to 64 μg/mL. Versiamide A showed antibacterial activity against *Aeromonas hydrophila*, *E. coli*, *Micrococcus luteus* and *P. aeruginosa*, with MIC values of 64, 16, 64 and 64 μg/mL. 3, 15-dehydroprotuboxepin K showed antibacterial activity against *E. tarda*, *E. coli*, *M. luteus*, *P. aeruginosa* and *V. harveyi*, with MIC values of 64, 8, 16, 32 and 64 μg/mL [59].

An antibacterial terpenoid, namely terretonin F (**28**), were isolated from the *Aspergillus* sp. RR-YLW12, which derived from marine red algae *R. confervoide*. Terretonin F showed significant inhibitory activities against *Chattonella marina*, *Heterosigma akashiwo* and *Prorocentrum donghaiense*, with IC50 values of 3.1, 5.2 and 10.5 μg/mL, respectively [60].

In conclusion, *Aspergillus* species from marine algae and active metabolites were summarized. Five antimicrobial compounds were found in three fungi strains of algae origin. It should be noted that asperglaucins A and B (**24** and **25**) showed a strong inhibitory effect on *B. cereus*. The possible bacteriostatic mechanism of the compounds was also introduced. At present, the studies on the structure and biological activity of compounds are abundant, but the studies on the mechanism of biological activity are limited.
