B pharm sem VII, Pharmacognosy, Shivaji university, Kolhapur MS

1. Pradnya Wadekar Bapat,
Asst. Professor,
ABCP, Sangli

2.  Definition: Drug that are pharmacologically inactive
but when exposed to UV- radiation or sunlight
converted to their active metabolite to produce a
beneficial reaction affecting the diseased tissue.
 The photosensitizing agent has property to
fluorescence. On exposure to visible light it absorbs a
quantum of energy and the molecule becomes
activated.
 This energy is transferred to other molecules such as
amino acids, histamine, tryptophan and tyrosine,
which in turn become activated; subsequently
decompose or undergo further chemical reactions.
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3. Photosensitizing reactions
PHOTOALLERGY
PHOTOPHOBIA
PHOTOTOXICITY
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4.  Photoallergy is an allergic reaction of the skin
to UV light.
 Photophobia is a fear or strong desire to avoid
all light sources based on a painful sensitivity of
the eyes to strong light.
 Phototoxicity is an irritation of the skin after
exposure to UV light. immediate reactions may
include itching, burning, swelling, scaling and
rashes.
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5. CLASSIFICATION OF
PHOTOSENSITIZER
PHOTODYNAMIC PHOTOSENSITIZING
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6. PHOTODYNAMIC PHOTOSENSITIZER
 Photodynamic agents require oxygen for their
action.
 This group include photodynamic dyes, hypericin,
phagopyrin, bengal rose, erythrosine, quinin,
methylene blue, prophyrin.
 These substances photo-oxidize terpenene, blood
serum and cause haemolysis.
 They are topically inactive but on intra-dermal
injection causes immediate photoreaction of
short duration.
 The decrease in temperature of irradiation
inhibits the photosensitization effect.
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7. PHOTOSENSITIZING PHOTOSENSITIZER
 It do not require oxygen for reaction.
 These photosensitizing agents include
furanocoumarins and their derivatives.
 These compound neither cause photo-oxidation of
terpenene nor haemolysis.
 Temperature of irradiation has no effect on
photosensitization activity of these compounds.
 Photosensitizer combined with ultraviolet light may
also contribute to other health problems, including
skin cancer, photoaging and allergic reactions.
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8. Photodynamic Photosensitizing
Require oxygen for their action,
e.g. Quinine, acridine dye.
Do not require oxygen for eaction.
E.g. Psoralen, xanthotoxin.
Photosensitizing effect: Erythema
produced, appears immediately
after irradiation & disappear a
few hrs.
Erythema produced by
furanocoumarin appears after
several hr and last for several days
The decrease in temperature of
irradiation inhibits
photosensitization effect.
Temperature of irradiation has no
effect on activity of those
compounds.
Naturally occuring or may be
syntehtic pigments or dyes
Naturally occuring in plants
belonging to family Umbelliferae
and rutaceae
They oxidize terpens, serum
proteins and unsaturated fatty
acids -> heamolysis
Don’t oxides terpens, serum
proteins and unsturated fatty ->
no heamolysis
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9. Photosensitizing subsatnces
 Buck wheat
 Alsike clover- commonly seen in horses
 Kochia scoparia ie kochia weed
 Lupines
 Mouldy straw
 Lady’s thumb
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10. PHOTOSENSEITIZING AGENTS IN
THERAPY
 Use in treatment of vitiligo disease, in which melanin
formation is deficient.
 Extract of Ammi majus L or juice of the fruits of
Psoralea corylifolia, that have long been used in
treatment of vitiligo.
 Extract is either given orally or painted on the
unpigmented spot of the patient.
 The patient is then exposed to sunlight for 1-2 hrs.
 Development of a strong brown color after 2 days.
 The joint action of medicine and irradiation, is called
photochemotherapy.
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11. PHOTODYAMIC THERAPY
 Photodynamic therapy (PDT) is based on the
discovery that certain chemicals can kill one
cell in the presence of light.
 PDT is as a bio-component therapy method.
 PDT method for treatment of tumor diseases
using original domestic photosensitizing
agents.
 Selectivity of PDT effect on malignant tissues is
ensured primarily through accumulation of
photosensitizing agents and pro-sensitizer in
tumor tissues due to more intensive blood
supply of tumors.
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12. FUNGAL TOXIN Mycotoxin are chemicals produced by fungi, molds under
certain conditions.
 They are essential for fungal growth and reproduction and
toxic to human and animals.
 More than 250 toxins
 Disease caused by mycotoxins are called mycotoxicosis.
 Disease caused by mold infection are called mycosis.
 The reason for the production of mycotoxins is not yet
known; they are not necessary for the growth or the
development of the fungi. Because mycotoxins weaken the
receiving host, the fungus may use them as a strategy to
better the environment for further fungal proliferation. The
production of toxins depends on the surrounding intrinsic
and extrinsic environments and these substances vary
greatly in their toxicity, depending on the organism infected
and its susceptibility, metabolism, and defense mechanisms
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13. AFLATOXIN
 Aflatoxin is produced by Aspergillus parasiticus
and A. flavus.
 There are 5 important aflatoxins called
aflatoxin B1,B2,G1,G2 and M.
 Aflatoxins are extremely toxic and their target
organ is liver.
 Aflatoxin B1 is three times more toxic than G1
and is the most potent naturally occurring
hepatocarcinogen.
 Aflatoxin exposure depresses the immune
system and may cause abortion.
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14. STEARIGMATOCYSTIN
 It is produced by certain species of
Aspergillus versicolor.
 The toxic effects of sterigmatocystin are
much the same as those of aflatoxin B1.
 It is thus considered as a potent
carcinogen,mutagen, and teratogen.
 Toxic effects of sterigmatocystin-fed
laboratory animals have included kidney
and liver damage and diarrhoea.
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15. ERGOTOXIN
 Ergot or ergot fungi refers to a group of fungi of
the genus Claviceps.
 The most prominent member of this group is
Claviceps purpurea. This fungus grows on rye and
related plants, and produces alkaloids that can
cause ergotismin humans and other mammals.
 The neurotropic activities of the ergot alkaloids
may also cause hallucinations.
 Ergot cause CNS and peripheral disorders.
 It cause tangerine and abortion in pregnant
females.
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16. OCHRATOXIN
 It is produced by Aspergillus ochraceus and
even by penicilium viridicatum .
 Ochratoxin A has been associated the
disease known balkan nephropathy.
 Ochratoxin formation is favoured by cold
temperature below 50º F and has been
found on cheese cake.
 The target organ seems to be kidney
followed by liver. Ochratoxin B is non-toxic.
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17. Citrinin
 is a toxin that was first isolated from Penicillium
citrinum, but has been identified in over a
dozen species of Penicillium and several species
of Aspergillus.
 Some of these species are used to produce
human foodstuffs such as cheese, sake, miso,
and soy sauce.
 Citrinin is associated with yellowed rice
disease in Japan and acts as a nephrotoxin.
 Citrinin can also act synergistically with
Ochratoxin A to depress RNA synthesis in
murine kidneys.
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18. Patulin
 is a toxin produced by the P.
expansum, Aspergillus, Penicillium,
and Paecilomyces fungal species.
 P. expansum is especially associated with a
range of moldy fruits and vegetables, in
particular rotting apples and figs.
 It is destroyed by the fermentation process and
so is not found in apple beverages, such
as cider.
 Although patulin has not been shown to be
carcinogenic, it has been reported to damage
the immune system in animals.
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