American Journal of Plant Sciences, 2013, 4, 1941-1948 Published Online October 2013 (
Chemical Analysis of Carica papaya L. Crude Latex
Jeana S. Macalood*, Helen J. Vicente, Renato D. Boniao, Jessie G. Gorospe, Elnor C. Roa
Mindanao State University at Naawan, Naawan, Misamis Oriental, Philippines.
Email: *
Received July 11th, 2013; revised August 11th, 2013; accepted September 15th, 2013
Copyright © 2013 Jeana S. Macalood et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Crude latex of Carica papaya L. has been known to offer a lot of benefits and potentials especially in the agricultural
industry and human health. This study focuses on the latex coming from its fruits of Papaya CX variety. Seven to eight
longitudinal incisions were made in order to allow latex to appear and drain in the collecting devices. 439.5 g dried la-
tex was stored in plastic containers and freezed. Results showed that dried latex contained higher amount of crude pro-
tein (57.24 ± 0.69%), followed by moisture (17.76 ± 0.09%), ash (7.00 ± 0.01%), crude fat (5.21 ± 0.13%) and crude
fiber (0.67 ± 0.09%) based on the complete proximate analysis. In the enzyme analysis, papain had protease activity of
2655 units·g1 at pH 5.5 and 285 units·g1 at pH 9.0. These results provided evidence that papain as a protease enzyme
is found in the crude latex of papaya which is a major constituent in various proteolytic activities. Crude latex from C.
papaya L. can be utilized to address the issues in agricultural farms to accelerate production and reduce environmental
Keywords: Carica papaya; Papaya CX Variety; Latex; Protease Activity; Papain; Complete Proximate Analysis
1. Introduction
Latex-bearing plants are believed to provide protection
against the attack of herbivores. Latex is known to com-
pose of various kinds of proteins including enzymes
which interact with the cellular aspect of the host insects
resulting in growth inhibition, physiological damages and
mortality. This prompted much research endeavour aim-
ing to provide exact information on the defense mecha-
nisms offered by the constituting compounds among
lateces. Many of these compounds provide resistance to
herbivores via toxicity or antinutritive effects, whereas
others are involved in the stickiness that can mire insect
herbivores [1]. These defense-related components appear-
ing in latex of distant phylogenetic groups are thought to
have possible biological effects on herbivores. Among
these compounds are the proteases which have shown
toxicological effects on insects. Proteases from a variety
of sources (viruses, bacteria, fungi, plants, and insects)
have toxicity towards insects [2]. Some of these insecti-
cidal proteases evolved as venom components, herbivore
resistance factors, or microbial pathogenicity factors,
while other proteases play roles in insect development or
digestion, but exert an insecticidal effect when over-ex-
pressed from genetically engineered plants or microbial
Many of these proteases are cysteine proteases, al-
though insect-toxic metalloproteases and serine proteases
have also been examined [2]. Cysteine proteases are re-
ported from latex of plant families such as Caricaceae,
Moraceae and Apocynaceae [3,4]. In addition, some la-
tex proteins are confined to specific plant taxa and have
been suggested to be involved in plant defense. These
compounds include phosphatase in Euphorbiaceae [5];
lipase in Caricaceae, Euphorbiaceae, Apocynaceae [6-8];
and glutaminyl cyclase in Caricaceae (papaya) [9,10]. Ca-
rica papaya Linn. being a monoecious, dioecious or her-
maphrodite tree is the most common species of the fam-
ily Caricaceae [11,12]. Carica papaya preparations can be
efficiently used in tissue burn and microbial/helmintic in-
fection. It can be also used as insecticidal/molluscicidal
activity against various pests [13]. This plant contains
specialized cells (laticifers) dispersed throughout most
plant tissues that secrete “latex” [14]. Papaya latex is a
thixotropic fluid with a milky appearance that contains
about 85% water. An insoluble particulate fraction whose
composition is still practically unknown, makes up 25%
of the dry matter. The soluble fraction, however, contains
both the usual ingredients such as carbohydrates (~10%),
salts (~10%) and lipids (~5%), and representative biomo-
lecules such as glutathione, cysteine proteinases (~30%)
*Corresponding author.
Copyright © 2013 SciRes. AJPS
Chemical Analysis of Carica papaya L. Crude Latex
and several other proteins. Consequently, the resulting
non-water-soluble material is generally considered as
waste, and in comparison to the water soluble fraction,
little is known regarding its chemical composition [15].
Moreover, the levels of these enzymes vary in the fruit,
latex, seeds, leaves and roots [16]. Besides, female trees
have been found to differ in the amounts of the com-
pounds produced. Moreover, C. papaya is among the few
latex-bearing plants whose noxious chemical contents
have not been reported [17].
The objective of this study is to characterize the che-
mical constituents of C. papaya L. crude latex in terms of
proteins and proteases which are the plant defence against
herbivorous insects negatively affecting agricultural pro-
2. Materials and Methods
2.1. Study Area
Carica papaya L. plantation is located at Tiwi-Simanok,
Linangkayan, Naawan, Misamis Oriental which is 1 km
from the national high way of Naawan, Misamis Oriental
(Figure 1) and can be reached in a 10 min drive from the
poblacion. The plantation site is approximately 2 ha land
Figure 1. Carica papaya L. plantation at Tiwi-Simanok, Li-
nangkayan, Naawan, Misamis Oriental.
partly planted with coconut, banana and bamboos along
the mangrove swamp. This site was formerly utilized as a
cornfield with coconuts planted in between (Figure 2).
Linangkayan is one of the outlying areas among the 10
barangays covering the municipality of Naawan, Misa-
mis Oriental. These barangays remain to be rural areas
with 2370 residents in Linangkayan in 2007 and are cha-
racterized by dry and wet climate. Linangkayan, being
coastal is composed partly of sandy loam soil. The plain
areas of Linangkayan are mostly planted with coconut,
bananas with some trees and bamboos.
2.2. Collection of Latex
Latex of C. papaya L. was collected from locally grown
plants in Tiwi-Simanok, Linangkayan, Naawan, Misamis
Oriental (Figure 2). Flowers, fruits and whole plant pic-
tures of C. papaya L. species of papaya CX variety from
Del Monte, Phils. were sent to the National Museum of
the Phils., Manila for verification. The same plants were
used as latex source throughout the study. Fresh latex
was collected from locally grown C. papaya. Initially, 4
to 6 longitudinal incisions at 3 mm deep were made on
the unripe mature fruit surface from fruit stalk end to the
tip of the fruit by using a stainless steel knife between
0600 and 0800 h during bright sunshine [18,19]. The
incisions were repeated 4 times at 3 da interval. The ex-
uded latex was allowed to run down the fruit and drip
into collecting devices (aluminum trays) raised in the
trunk (Figures 3-5).
Figure 2. Carica papaya L. plantation at Tiwi-Simanok, Li-
nangkayan, Naaw an, Mi samis Oriental (Actual site).
Copyright © 2013 SciRes. AJPS
Chemical Analysis of Carica papaya L. Crude Latex 1943
Figure 3. Carica papaya L. latex collection by incision using
stainless steel knife.
Figure 4. Carica papaya L. latex allowed to drip in the alu-
minum tray raised in the trunk.
2.3. Isolation of Latex from C. papaya
The collected latex was spread on trays and left for dry-
ing through solar at 40˚C for 14 h (Figures 6 and 7).
With the aid of laboratory mortal and pestle, the latex
was ground producing a greenish or grey powder known
Collection of latex
(Kamalkumar, et al., 2007; Nitsawang, et al.,
Attaching aluminum trays on the C. papaya
trunk (Kamalkumar, et al., 2007; Nitsawang,
et al., 2006)
Dripping of exuded latex into aluminum trays
(Kamalkumar, et al., 2007; Nitsawang, et al.,
Isolation of latex
(Narinesingh and Maraj, 1989)
Spreading of latex on the trays
(Adu, et al., 2009)
Oven/Sun Drying
(40˚C for 14 h) (Adu, et al., 2009)
(mortar and pestle) (Adu, et al., 2009)
Papain storage
Storing in plastic bottles (20 g each) and
freezing of dried latex (refrigerator) for
chemical analysis (Narinesingh and Maraj,
Incisions at 3 mm deep on mature C. papaya
Fruit (Kamalkumar, et al., 2007;Nitsawang, et
al., 2006)
(Nitsawang, et al., 2006; Kamalkumar, et al.,
Figure 5. Flow chart of the methods involved in the study.
as papain [20] which is known to have a proteolytic ac-
tivity slightly higher than that of the fresh latex [21].
2.4. Analysis of Dried Latex Sample
A 100 g of C. papaya L. crude latex was taken for com-
plete proximate analysis and an additional of 10 g for
papain-enzyme. The variety of papaya used in the study
is papaya CX from Del Monte Philippines, Cagayan de
Oro City and its verified scientific name is Carica pa-
paya L. of the Caricaceae family. Dried latex sample of
100 g and 10 g were transferred separately to plastic con-
tainers and brought to Biotech Phils., UPLB, Laguna, for
complete proximate analysis in order to determine the
Copyright © 2013 SciRes. AJPS
Chemical Analysis of Carica papaya L. Crude Latex
Figure 6. Spreading of C. papaya crude latex on aluminium
Figure 7. Solar and air drying of C. papaya crude latex at
30˚C - 40˚C.
components and protease activity, respectively. Protease
activity was employed utilizing the Hammersten casein
as substrate. The sample was passed unto 60 mesh sieve
to obtain uniform sample size. Approximately 0.12 g
sample was weighed and 10 mL of each buffer was
added. The mixture was stirred for 30 min and then cen-
trifuged for 5 min at 12,000 rpm to obtain a clear super-
natant and then diluted with the same buffer. The diluted
enzyme solution was allowed to react with the substrate
of desired pH for 10 min at 55˚C. The reaction was stop-
ped by addition of trichloroacetic acetic acid and the
amount of tyrosine released was determined spectropho-
tometrically using a standard curve at 280 nm. Analysis
was based on one unit of protease activity which releases
1.0 micromole of tyrosine min1 from 0.5% Hammersten
casein in 0.2 M acetate buffer pH 5.5 and 0.2 M glycine-
NaOH buffer pH 9.0 at 55˚C.
2.5. Papain Storage
The dried products were packed in air-tight plastic con-
tainers and stored in a cool, dry place. Four plastic con-
tainers at 100 g capacity were used to pack crude papain
flakes or powder since metal containers would result in
loss of enzyme activity (Figure 8). These were kept and
stored in freezer at 20˚C [18] in order to avoid reduc-
tion of its shelf life (Figure 9). Native and modified pa-
pain preparations were stored at 25˚C and 45˚C, and en-
zymatic activity was measured at scheduled times. It is
generally accepted that a month’s stability of an enzyme
at 45˚C is roughly equal to that of one year at room tem-
perature [22]. The latex from these unripe fruits pre-
sented a high activity compared with the fruit skin. Un-
der the temperature evaluated conditions does not exist a
significant statistic difference for the specific enzymatic
activity for the selected drying processes. The only main
difference presented was obtained according to the latex
source [23].
Figure 8. Flakes-formed crude latex of C. papaya in plastic
Figure 9. C. papaya dried crude latex stored-freeze in plastic
Copyright © 2013 SciRes. AJPS
Chemical Analysis of Carica papaya L. Crude Latex 1945
2.6. Disposal
All trays and other materials used in the latex collection
and drying were washed thoroughly with water and de-
tergent soap and kept dried. Waste water was allowed to
run to the sink.
2.7. Documentation
The whole process in the latex characterization was do-
cumented by using a DSC-S950 Sony digital camera.
3. Results
Complete proximate analysis of C. papaya L. dried latex
showed that it contained higher amount of crude protein
at approximately (57.24 ± 0.69%) over other components
such as moisture (17.76 ± 0.09%), ash (7.00 ± 0.01%),
crude fat (5.21 ±0.13%) and crude fiber (0.67 ± 0.09%)
(Table 1).
The enzyme-crude papain activity of the dried crude
latex of C. papaya L. showed that at pH 5.5 protease ac-
tivity yielded 2655 units·g1 and at pH 9.0 protease ac-
tivity yielded 285 units·g1 only (Table 2). The remain-
ing brownish-white flakes formed of C. papaya dried
crude latex were packed and stored freeze in 4 plastic
containers with a capacity of approximately 100 g con-
tainer1 (Figures 8 and 9).
4. Discussion
Proximate analysis of dried crude latex of Carica papaya
Linn of papaya CX variety revealed high amount of
crude protein (57.24 ± 0.69%) with moisture (17.76 ±
0.09% ), ash (7.00 ± 0.01%), crude fat (5.21 ± 0.13%)
Table 1. Complete proximate analysis of dried crude latex
of Carica papaya L.
Crude Fat
Dried latex
57.24 ±
17.76 ±
7.00 ±
5.21 ±
0.67 ±
Table 2. Protease activity analysis of dried crude latex of
Carica papaya L.
Protease activity*
Sample Code Biotech
Code pH 5.5 pH 9.0
Dried crude
latex from
Carica papaya
(crude papain)
P-1301 2655 units·g1 285 units·g1
*One unit of protease activity is defined as the amount of enzyme that re-
leases 1.0 micromole of tyrosine per minute from 0.5% Hammersten casein
in 0.2 M acetate buffer pH 5.5 and 0.2 M glycine-NaOH buffer pH 9.0 at
and crude fiber (0.67 ± 0.09%) (Table 1). Relatively,
latex is a milky fluid with a complex mixture of consti-
tuents, like proteins, vitamins, carbohydrates, lipids, ter-
penes, alkaloids, and free amino acids [24]. The presence
of certain enzymes like chitinases and proteases in latex
vacuoles suggests that they may help plants for defense
against pathogens, parasites, and herbivores by attacking
the invader once the plant cell is lysed [25]. Proteases are
enzymes that catalyze the degradation of peptides and
proteins. Proteases have significant role in numerous
physiologic processes in the living organisms, as well as
in different industrial processes. It was verified that pro-
teases that are direct specific and selective modifications
of proteins, such as the activation of proenzymes, san-
guineous coagulation, digestion of fibrin clots, secretory
protein processing and transport through membranes,
germination, senescense, defense against plant pathogens
(especially fungi and insects), and acquisition of nutri-
ents and apoptosis [26-32]. Other previous papaya latex
researches reported that the plants are rich in cysteine
proteinases enzymes. These enzymes are used widely for
protein digestion functions in the food and pharmaceuti-
cal industries [33]. Furthermore, cysteine proteases have
traditionally been viewed as lysosomal mediators of ter-
minal protein degradation and enzymes that catalyze hy-
drolysis of amide bonds [34]. Basically, cysteine prote-
ases are classified into various kinds and one of which is
papain, a plant proteolytic enzyme for the cysteine pro-
teinase family. Cysteine protease enzyme is found natu-
rally in papaya (C. papaya L.) manufactured from the
latex of raw papaya fruits. The enzyme is able to break
down organic molecules made of amino acids, known as
polypeptides and thus plays a crucial role in diverse bio-
logical processes in physiological and pathological states,
drug designs and industrial uses [35] and the enzyme is
the most thoroughly characterized of the thiol proteinases
[36]. Papain has revealed to be an enzymatic protein of
significant biological and economic importance, since the
unique structure of papain provides functionality and
helps explain how this proteolytic enzyme works and
makes it valuable for a variety of purposes [35]. This
proteolytic enzyme usually consists of two well-defined
domains which provide an excellent system for studies in
understanding the folding-unfolding behavior of proteins
[37]. The protein is stabilized by three disulfide bridges
in which the molecule is folded along these bridges cre-
ating a strong interaction among the side chains which
contributes to the stability of the enzyme [38,39]. Its
three-dimensional structure consists of two distinct
structural domains with a cleft between them. This cleft
contains the active site, which contains a catalytic diad
that has been likened to the catalytic triad of chymotryp-
sin [35]. Papain occurs in all parts of the tree except the
root [40]. A well managed papaya production has re-
Copyright © 2013 SciRes. AJPS
Chemical Analysis of Carica papaya L. Crude Latex
corded higher papain yield of 8.17 g·fruit1 and highest
papain of 686.29 g·plant1 in a period of 6 mo [35]. As to
the analysis of the protease activity, results showed that
papain at pH 5.5 had a protease activity of 2655 units·g1
and 285 units·g1 only at pH 9.0 (Table 2). The results
imply that papain is more active in its activity in slightly
acidic medium than in a basic. Several studies supported
the idea as papain exhibits its greatest activity at an acid-
ity equal to the concentration of the hydrogen ion of 105
N; i.e., slightly more acid than is necessary to cause
methyl red to change from yellow to red [41]. It is the de-
finite hydrogen ion concentration at which papain was
most active proteolytically. The conditions of acidity for
the optimum action of papain are found to be pH = 5 [41].
Plant-based enzymes, such as bromelain from pineapple
and papain from papaya, have proteolytic activity [42].
Papain as a cysteine hydrolase is stable and active under
a wide range of conditions. It is very stable even at ele-
vated temperatures [43]. Papain is unusually defiant to
high concentrations of denaturing agents, such as, 8 M
urea or organic solvent like 70% EtOH [38,44]. The en-
zyme has been reported to be generally more stable in
hydrophobic solvents and at lower water contents and
can catalyze reactions under a variety of conditions in
organic solvents with its substrate specificity little chang-
ed from that in aqueous media [45]. However, most cys-
teine proteases are unstable and weakly active at neutral
pH and thus are optimized to function in acidic intracel-
lular vesicles [34]. Optimum pH for activity of papain is
in the range of 3.0 - 9.0 which varies with different sub-
strate [39,44]. Under the temperature evaluated condi-
tions does not exist a significant statistic difference for
the specific enzymatic activity for the selected drying
processes. The only main difference presented was ob-
tained according to the latex source [23]. Papain being
solubilized in water showed greater enzymatic activity
[46]. Besides, the hydrolytic activity of the latex de-
pended upon the state of development of the fruit [47].
Almost ripe fruits yielded latex which split only proteins
and was without effect on peptones, whereas latex from
unripe fruits showed activity towards both proteins and
peptones, and latex from very young fruits showed “full
activity”. The greener the fruit, more active is the papain
5. Summary and Conclusion
1. The collection and the isolation of crude dried latex
of Carica papaya L. were done for chemical analysis
characterizing its protein and proteases as the constitu-
ents for plant defence against herbivores insects.
2. Complete proximate analysis of dried crude latex of
Carica papaya L. showed that it contained higher con-
centration of crude protein (57.24 ± 0.69%) followed by
moisture (17.76 ± 0.09%), ash (7.00 ± 0.01%), crude fat
(5.21 ± 0.13%) and crude fiber (0.67 ± 0.09%).
3. A protease activity of 2655 units·g1 was obtained at
pH 5.5 and 285 units·g1 only at pH 9.0.
4. Crude latex of C. papaya could be highly consid-
ered a potential source for proteolysis especially when
applied in slightly acidic medium where its protease ac-
tivity is much higher.
5. The protease activity analysis was especially focus-
sed on the crude papain content of the carica papaya la-
6. Evidently, papain is one of the protease enzymes
being noted to have been significantly employed or ac-
tively participated in many proteolytic activities which
could be beneficial when applied in farms addressing the
many hazardous environmental issues like pollution, de-
gradation, pest control, health problem and many others.
6. Implications and Recommendations
Chemical analysis of Carica papaya L. crude latex re-
vealed the presence of crude proteins in higher amount as
compared to other chemical constituents. Protease en-
zyme being protein in nature showed a higher protease
activity of 2655 units·g1 at pH 5.5 and 285 units·g1
only at pH 9.0. These results implied that proteolysis of
crude latex from C. papaya L. could be more effective
when applied in slightly acidic medium than in a basic.
This study suggests the potential of C. papaya L. crude
latex in the control of pest population that ensues declin-
ing farm production. There shall be more studies involv-
ing crude latex of C. papa ya on its action to other plants
and also to the insects’ morphological formations. Fur-
thermore, this study can serve as a reference among re-
searchers to continue investigating more valuable infor-
mation on the potentials offered by C. papaya L. to im-
prove farm production and resolved issues on environ-
mental degradation and health related problems. More-
over, this study will boost agricultural production using
crude latex of C. papaya as pest control knowing its pro-
tein contents and its protease activity.
7. Acknowledgements
This work was supported financially by the Department
of Agriculture-Bureau of Agricultural Research (DA-
BAR), Manila. Secretary Imelda M. Nicolas of the Ex-
change Visitor Program (EVP) for the dissertation grant
extended under the enhancement training sponsorship
project. Special thanks RomyRico B. Roa and company
of Patag, Naawan, Misamis Oriental for the use of the
papaya farm as the source of latex collection.
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