Date of Award

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biotechnology Science and Engineering

Committee Chair

William N. Setzer

Committee Member

Debra M. Moriarity

Committee Member

Bernhard Vogler

Committee Member

Leland Cseke

Committee Member

Ifedayo V. Ogungbe

Subject(s)

Natural products., Pharmacognosy., Cell-mediated cytotoxicity.

Abstract

Natural products have been used in traditional medicine throughout history. All drugs and medicinal agents were derived from natural substances or inspired by a natural product. The major source of these remedies is higher plants which are great sources for new compounds that have a wide variety of activity. Conradina canescens Gray (false rosemary) is a common evergreen shrub, endemic to a small area of west Florida and adjacent Alabama and southern parts of Mississippi, USA. There are very limited studies on the chemical composition of this plant species. According to the available literature, this species has not been tested for bioactivity or cytotoxicity, except for allelopathy. In this work, the essential oil was isolated using hydrodistillation and was analyzed using GC/MS. The essential oil of C. canescens was found to be rich in monoterpenoids, particularly 1,8-cineole, myrtenal, p-cymene, camphor, myrtenol, myrtenyl acetate, and α-pinene. C. canescens oil was screened for antimicrobial activity and cytotoxic activity but was found to be inactive. However, the oil showed remarkable allelopathic effects on both Lactuca sativa and Lolium perenne. Because its oil chemical composition is comparable to rosemary, C. canescens may be a useful and beneficial herb. A total of six compounds, namely ursolic acid (62.40%), betulin (8.41%), β-amyrin (4.60%), myrtenic acid (2.88%), n-tetracosane (1.44%), and oleanolic acid (1.05%), were isolated. The structures of the isolated compounds were established by spectroscopic studies using NMR and IR spectroscopy. The crude extract and isolated compounds were subjected to cytotoxicity, antimicrobial and antileishmanial bioassays. The crude extract showed substantial cytotoxic, antimicrobial and antileishmanial activities. Ursolic acid and betulin showed significant cytotoxic effects against human breast cancer (MCF-7 and MDA-MB-231) and bladder cancer (5637) cell lines emphasizing a medicinal importance of the plant. n-Tetracosane exhibited the most antibacterial activity while myrtenic acid showed the highest antifungal activity. Almost all the tested compounds, except betulin and n-tetracosane, showed significant germination inhibition of both L. sativa and L. perenne in a concentration-dependent manner, with ursolic acid being the most active. The results of the current study emphasize the potential medicinal and economic importance of C. canescens.

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