**4. Developing new therapeutic agents via modulation of biological systems using phenolic compounds**

Over 15 years, FAB-Lab team had developed several models for designing new therapeutic agents from phenolic compounds through inhibiting different target enzymes.

#### **4.1 Tyrosinase**

Flavonoids contain an alpha-keto group as new type of tyrosinase inhibitors from natural products as potential treatments for hyperpigmentation [28].

#### **4.2 Hyalourindase**

The extract of different organs of *Ravenala madagascariensis* (Sonn.) plant showed a good inhibitory activity against hyaluronidase enzyme. Both metabolic analysis and phytochemical studies disclosed the presence of 19 different phenolic compounds, which may present flavone, flavonol, and flavanol glycosides, and aglycone. Specifically, isorhamnetin-7-O-rutinoside, rutin, epiafzelechin, kaempferol, isorhamnetin 7-O-glucoside, and narcissin were isolated and characterized from the butanolic extract of leaves. In docking experiments, narcissin, quercetin 3-O-glucoside, and rutin may interact with enzymes via H-bonding with the Asp111, Gln271, and/or Glu113 residues. These interesting results could be used in pharmaceutical industry to develop new therapeutic agent(s) for skin wrinkles and other cosmetic purposes [29].

#### **4.3 Aldose reductase**

The olive and ginkgo leaves extracts with high phenolic contents was proved in an *in vitro* and *ex vivo* inhibitory activity against aldose reductase and could be used as promising therapy for cataract [30, 31].

#### **4.4 Leukotriene hydrolyase**

Leukotriene hydrolyase LT4: Synthesis, docking, cytotoxicity, and LTA4H inhibitory activity of phenolic gingerol derivatives as potential colorectal cancer therapy [32, 33].

*Research on Natural Phenolic Compounds in FAB-Lab: Nonconventional Industrial… DOI: http://dx.doi.org/10.5772/intechopen.101446*

#### **Figure 4.**

*Developing luteolin-7-O-α-L-rhamnoside as a promiscuous multitarget enzyme inhibitors at three different sites of amylase (A), tyrosinase (B), and hyaluronidase (C). Rationale for the multitarget (promiscuous) inhibitory activity of luteolin-7-O-α-L-rhamnoside (D) and possible action of luteolin-7-O-α-L-rhamnoside (E).*

### **4.5 Promiscuous multitarget inhibitors for treatment of chronic and complicated health disorders**

Phenolic compounds proved to be safe and effective multitarget enzyme inhibitors. Screening of over 50 medicinal plant extracts revealed that the phenolic contents of *Punica granatum*, *Phyllanthus emblica*, and *P. guajava* showed good inhibitory activity on α-amylase tyrosinase and hyaluronidase enzymes (as shown in **Figure 4**). These raw data encouraged us in FAB-Lab to go further to develop and design a multitarget drug from phenolic compounds [34–36].
