The use of and search for drugs and dietary supplements derived from plants have accelerated in recent years. Ethnopharmacologists, botanists, microbiologists, and natural-products chemists are combing the Earth for phytochemicals and “leads” which could be developed for treatment of infectious diseases. While 25 to 50% of current pharmaceuticals are derived from plants, none are used as antimicrobials. Traditional healers have long used plants to prevent or cure infectious conditions; Western medicine is trying to duplicate their successes. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids, and flavonoids, which have been found in vitro to have antimicrobial properties. This review attempts to summarize the current status of botanical screening efforts, as well as in vivo studies of their effectiveness and toxicity. The structure and antimicrobial properties of phytochemicals are also addressed. Since many of these compounds are currently available as unregulated botanical preparations and their use by the public is increasing rapidly, clinicians need to consider the consequences of patients self-medicating with these preparations.

Plant Products as Antimicrobial Agents

http://www.dietcan.net/docs/Polifenoles%20en%20alimentos%20y%20biodisponibilidad.pdf

Polyphenols: food sources and bioavailability

The therapeutic properties of light have been known for thousands of years, but it was only in the last century that photodynamic therapy (PDT) was developed. At present, PDT is being tested in the clinic for use in oncology--to treat cancers of the head and neck, brain, lung, pancreas, intraperitoneal cavity, breast, prostate and skin. How does PDT work, and how can it be used to treat cancer and other diseases?

Photodynamic therapy for cancer

Resveratrol, a phytoalexin found in grapes and other food products, was purified and shown to have cancer chemopreventive activity in assays representing three major stages of carcinogenesis. Resveratrol was found to act as an antioxidant and antimutagen and to induce phase II drug-metabolizing enzymes (anti-initiation activity); it mediated anti-inflammatory effects and inhibited cyclooxygenase and hydroperoxidase functions (antipromotion activity); and it induced human promyelocytic leukemia cell differentiation (antiprogression activity). In addition, it inhibited the development of preneoplastic lesions in carcinogen-treated mouse mammary glands in culture and inhibited tumorigenesis in a mouse skin cancer model. These data suggest that resveratrol, a common constituent of the human diet, merits investigation as a potential cancer chemopreventive agent in humans.

https://science.sciencemag.org/content/sci/275/5297/218.full.pdf

Cancer Chemopreventive Activity of Resveratrol, a Natural Product Derived from Grapes

Flavonoids are nearly ubiquitous in plants and are recognized as the pigments responsible for the colors of leaves, especially in autumn. They are rich in seeds, citrus fruits, olive oil, tea, and red wine. They are low molecular weight compounds composed of a three-ring structure with various substitutions. This basic structure is shared by tocopherols (vitamin E). Flavonoids can be subdivided according to the presence of an oxy group at position 4, a double bond between carbon atoms 2 and 3, or a hydroxyl group in position 3 of the C (middle) ring. These characteristics appear to also be required for best activity, especially antioxidant and antiproliferative, in the systems studied. The particular hydroxylation pattern of the B ring of the flavonoles increases their activities, especially in inhibition of mast cell secretion. Certain plants and spices containing flavonoids have been used for thousands of years in traditional Eastern medicine. In spite of the voluminous literature available, however, Western medicine has not yet used flavonoids therapeutically, even though their safety record is exceptional. Suggestions are made where such possibilities may be worth pursuing.

The Effects of Plant Flavonoids on Mammalian Cells:Implications for Inflammation, Heart Disease, and Cancer

Recent Studies on Biologically Active Natural Products

The human immunodeficiency virus type-1 (HIV-1) is the etiologic agent for acquired immunodeficiency syndrome (AIDS), which has reached pandemic proportions in recent years. A second immunodeficiency virus (designated HIV-2), which is serologically distinct from HIV-1, was later isolated from West African patients with AIDS. Research efforts have intensified in an attempt to discover new therapeutic modalities for the treatment of this fatal disease. The complex replication process of the HIV in its host cell offers many potential target points for therapeutic intervention. Examples include viral attachment and uncoating, reverse transcription of the viral genome, proviral DNA integration into the host cell DNA and subsequent transcription and translation of this genetic material into viral proteins. As these viral proteins in turn undergo processing, e.g., protein glycosylation, which then leads to the assembly and release of progeny virus particles, additional target points are obvious.

/pdf/screening-of-natural-products-as-hiv-1-and-hiv-2-reverse-3v0jq1ojm4.pdf

Screening of Natural Products as HIV-1 And HIV-2 Reverse Transcriptase (RT) Inhibitors

Improved fluorometric method for quantitative high-performance liquid chromatographic analysis of methylated guanine derivatives in DNA

Four novel stilbenes ( 1 – 4 ) were isolated from the root bark of Ekebergia benguelensis . The structures were established by spectroscopic methods including 2D NMR analysis. The structure of 1 , a new stilbene–coumarin hybrid representing a novel skeleton, was confirmed by single X-ray analysis. Compounds 1 – 4 were evaluated against a panel of human cancer cell lines.

Novel Stilbenes Isolated from the Root Bark of Ekebergia benguelensis.

From the leaves of Monotes engleri, five prenylated flavanones were isolated as constituents that displayed cytotoxic activity against several human cancer cell lines. Three of these substances are novel, namely, 6-(1,1-dimethylallyl)naringenin, 6-(1,1-dimethylallyl)eriodictyol and 3′-O-methyl-6-(1,1-dimethylallyl)eriodictyol, with the other two active substances being the known flavanones, 6,8-diprenyleriodictyol and hiravanone. Additionally, two novel, but non-cytotoxic, biogenetically related flavanones were isolated, 6-[(2RS)-hydroxy-3-methyl-3-butenyl]-8-prenyleriodictyol and 5,4′-dihydroxy-4″,4″-dimethyl-5″-methyl-5″H-dihydrofurano[2″,3″:6,7]flavanone. The structures of the new compounds were determined by spectral analysis 1D- and 2D-NMR experiments.

John M. Pezzuto

Papers

Recent Studies on Biologically Active Natural Products

Screening of Natural Products as HIV-1 And HIV-2 Reverse Transcriptase (RT) Inhibitors

Improved fluorometric method for quantitative high-performance liquid chromatographic analysis of methylated guanine derivatives in DNA

Novel Stilbenes Isolated from the Root Bark of Ekebergia benguelensis.

Cytotoxic Prenylated Flavanones from Monotes engleri.