ISSN (Online) 2249-6084 (Print) 2250-1029
International Journal of Pharmaceutical and
Phytopharmacological Research (eIJPPR)
[Impact Factor – 0.7826]
Research Article
Journal Homepage:
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HERBAL INDICATORS: AN ALTERNATIVE TO SYNTHETIC
INDICATORS
Kavitha G*, Chinju Sara George, Ancy Alex, Rakhi Raju, Rini Biju, Deepa T
Vasudevan
NAZARETH COLLEGE OF PHARMACY, DEPARTMENT OF PHARMACEUTICAL CHEMISTRY,
OTHERA, THIRUVALLA
* Corresponding author: kavithaamritha@gmail.com
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ABSTRACT
The pH indicators are used to show sharp color changes at intervals of pH.Natural pigments in
plants are highly colored substances and may show color change with variation of pH. An
attempt has been made to investigate the indicator activity of water extract of flower and fruit
pigments and to replace synthetic indicators, as they cause chemical pollution and are of high
cost. The water extract of Caesalpinia sappan, Caesalpiniaceae and Methanolic extract of Dahlia
pinnata, Asteraceae showed sharp and intense color change in acidic and basic medium. These
herbal indicators are evaluated by using strong acid- strong base, strong acid- weak base, weak
acid- strong base and weak acid – weak base titration. In all these titrations, the extract was
found to be very useful and accurate for indicating the equivalence point as the synthetic
indicators. The isolation of pure compounds possessing indicator properties helps to know the
mechanism by which they show indicator properties and new theories of indicators could be
established.
KEYWORDS-Synthetic indicators, Caesalpinia sappan, Dahlia pinnata, Herbal indicators
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1. INTRODUCTION
A pH indicator is something that can tell you whether a substance is an acid or a base. We often
notice the color changes that we see in the nature all around us. Many flowers, fruits and
vegetables contain chemical substances that changes color in the solutions of different pH. These
substances are known as natural pH indicators. All pH indicators change color depending on
whether they donate or accept protons. Therefore, pH indicators are themselves acids or bases1.
Dahlia pinnata (Asteraceae) is a yearly flowering plant and easily available in India and
elsewhere in high quantity and present in almost every garden to enhance their beauty2.
Caesalpinia sappan (Caesalpiniaceae) whose heartwood is widely being used in drinking water
for its anti-thirst, blood purifying, ant diabetic and several other properties is nowadays being
used as a coloring agent for wine, meat, fabric etc..As such, Sappan wood was a major trade
good during the 17th century when it was exported from South-east Asian nations aboard Red
seal ships to Japan3. Presently available acid-base indicators like phenolphthalein and methyl
orange are synthetic indicators which produce chemical hazards, availability problems and high
cost4,5. The present study is to investigate the indicator activity of Caesalpinia sappan and Dahlia
pinnata and to establish analytical applications.
2. MATERIALS AND METHODS
2.1 Plant materials
Fresh flowers of Dahlia pinnata (Asteraceae) and Heart wood of Caesalpinia sappan
(Caesalpiniaceae) were collected from Central Travancore.
2.2 Reagents
Analytical grade reagents like hydrochloric acid (HCl), Sodium hydroxide (NaOH), Acetic Acid
(CH3COOH), Ammonia (NH3) and phenolphthalein were used. The reagents and volumetric
solutions were prepared as per Indian Pharmacopoeia (IP 1996)6.
3.3 Methodology
The petals of the flower –Dahlia pinnata were cleaned by using distilled water and cut into small
pieces .Flower petals of 10g were shaken for an hour in 100 ml methanol7. The extract was
filtered to obtain a clear liquid. Heartwood of 10g sappan wood was boiled with 100ml water for
3 minutes and filtered. The extracts were preserved in a tightly closed glass container and stored
away from direct sunlight8.
The original pH of the indicators, indicator range9 and color of the indicators prepared in acid
(1M HCl) and base (1M NaOH) were tested. The chemical test for Anthocyanins10 was
performed for the prepared indicators. The analytical applications of prepared indicators were
confirmed by neutralization titrations11, 12.
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3. RESULTS AND DISCUSSION
The color of natural indicators prepared, Ph, color changes in acid and base, indicator range and
chemical test are indicated in table no 1. The color changes obtained in neutralization titrations
with different Titrants and titrates of 0.1 M are given in table no-2.The titre values in comparison
with synthetic indicator phenolphthalein are given in table no-3
For all types of titrations, equivalence point obtained by the aqueous extract of Caesalpinia
sappan either exactly coincided or very close with equivalence point obtained by standard
indicator phenolphthalein .These represents the usefulness of the extract as an indicator in acidbase titrations. The use of Dahlia pinnata in strong acid- strong base and weak acid – strong base
titrations was found to be more significant over standard indicator as it gives sharp color change
at equivalence point.
It is observed that the indicators act reversibly and give sharp color change in both directions.
The results obtained prove that the routinely used indicators can be replaced successfully by
plant extracts as they are simple, accurate
TABLE NO – 1 INDICATOR RANGE AND COLOR CHANGE OF HERBAL INDICATORS
PARAMETERS
DAHLIA PINNATA
1.pH
2.color of the
indicator
3.Color in acid
4.Color in base
5.Indicator range
6.Test for
Anthocyanins
5.55
Violet
CAESALPINIA
SAPPAN
6.2
Red
Pink
Green
3.5-7
Positive
Yellow
Pink
5.3-7.4
Negative
TABLE NO – 2 COLOR CHANGES IN NEUTRALIZATION TITRATIONS
INDICATOR
Dahlia pinnata
Dahlia pinnata
Dahlia pinnata
TITRANT
HCl
CH3COOH
HCl
COLOR
Pink
Pink
Pink
TITRATE
NaOH
NaOH
NH3
Dahlia pinnata
CH3COOH
NH3
Caesalpinia sappan
Caesalpinia sappan
Caesalpinia sappan
Caesalpinia sappan
HCl
CH3COOH
NH3
NH3
No visible color
change
Yellow
Yellow
Pink
Pink
4
NaOH
NaOH
HCl
CH3COOH
COLOR
Green
Green
No visible color
change
No visible color
change
Pink
Pink
Yellow
Yellow
TABLE NO – 3 COMPARISON WITH SYNTHETIC INDICATOR
CHEMICALS USED
TITRANT
TITRATE
HCl
CH3COOH
HCl
CH3COOH
NaOH
NaOH
NH3
NH3
VOLUMES OF TITRATES REQUIRED FOR
EQUIVALENCE POINT WITH TITRANT(25 ML)
WITH INDICATOR
STANDARD
DAHLIA
SAPPAN
INDICATOR
INDICATORS
WOOD
INDICATOR
25.1±0.2
24.4±0.43
24.2±0.37
24.5±0.35
24.8±0.28
24.3±0.40
24.8±1.02
24.6±0.44
25.0±0.40
25.6±0.52
4. CONCLUSION
In this study herbal indicators are prepared from Caesalpinia sappan and Dahlia pinnata by
simple procedures and the analytical applications were recorded. The presence of coloring
pigments anthocyanin in Dahlia pinnata and brazilin in Caesalpinia sappan may be responsible
for the indicator action. The isolation13 of pure compounds possessing indicator properties helps
to know the mechanism by which they show indicator properties and new theories of indicators
could be established.
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