Insecticidal fungi: Enzyme inhibitors extracted

Skip to Navigation

Ezine

  • Published: Nov 15, 2014
  • Author: David Bradley
  • Channels: NMR Knowledge Base
thumbnail image: Insecticidal fungi: Enzyme inhibitors extracted

Against the strain

Screening of dozens of strains of fungi that infect insects has led to the discovery of a strong inhibitor for the enzyme tyrosinase. Tyrosinase activity is involved in insect development processes but also in human aging, the development of melanoma, wound healing, and even in the browning of fruits and vegetables. (Cricket photo by David Bradley)

Screening of dozens of strains of fungi that infect insects has led to the discovery of a strong inhibitor for the enzyme tyrosinase. Tyrosinase activity is involved in insect development processes but also in human aging, the development of melanoma, wound healing, and even in the browning of fruits and vegetables.

Ruili Lu, Xiaoxiao Liu, Sha Gao, Wancun Zhang, Fan Peng, Fenglin Hu, Bo Huang, Longyun Chen, Guanhu Bao, Chunru Li and Zengzhi Li of Anhui Agricultural University, in Hefei, China, explain how the enzyme tyrosinase, which is also known as polyphenoloxidase, is a copper-containing oxidoreductase present in many mammals, insects, plants and microorganisms. It is the rate-limiting enzyme in the biosynthesis of the pigment melanin. Intriguingly, the enzyme's activity is related to a battle between insect and fungal pathogen - insects can risk infection by entomopathogenic fungi by a "browning" or "tanning" response while the fungi themselves can reduce the impact of this defensive function by blocking the protective browning.

Natural pesticides

This activity implies that tyrosinase inhibitors are likely to exist among the many secondary metabolites of entomopathogenic fungi and might be a useful source of natural insecticides. As such, the team has carried out screening of their entomopathogenic fungal library and they narrowed down the search to seven strains of Paecilomyces gunnii. They used preparative high-speed counter-current chromatography (HSCCC) with high-performance liquid chromatography (HPLC)-electrospray ionization (ESI)-high resolution mass spectrometry (HRMS) to isolate and purify the three most active compounds from their library and then proton and carbon-13 one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy to obtain structures for these compounds, paecilomycone A, B and C. Their structure activity relationship studies revealed that efficacy against tyrosinase relates positively to the compound having more hydroxyl groups.

Structured find

The team reports that the structure of paecilomycone A is very similar to the known anti-HIV target funalenone, a phenalenone. Those compounds are not only active against HIV, but have antibacterial, antitumour activity and activity against strains of malaria resistant to chloroquine drugs.

Entomogenous fungi have been probed for putative small molecule drug compounds among their secondary metabolites, but until now no tyrosinase inhibitors have been found. This work may well point the way to not only new types of natural insecticides based on the fungal defence activity that side-step the potential harm to mammals of neurotoxic pesticides, but may also lead to a range of new drugs for various infectious human diseases.

There are two additional areas in which the paecilomycones may find applications: as components of sun protection cosmetics where they enhance tanning and as "browning" agents for improve the aesthetics of manufactured food products.

Related Links

J Agric Food Chem 2014, online: "New tyrosinase inhibitors from Paecilomyces gunnii"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

Social Links

Share This Links

Bookmark and Share

Microsites

Suppliers Selection
Societies Selection

Banner Ad

Click here to see
all job opportunities

Most Viewed

Copyright Information

Interested in separation science? Visit our sister site separationsNOW.com

Copyright © 2017 John Wiley & Sons, Inc. All Rights Reserved